Regardless of whether you are buying instructions for a Lego custom designed model, or downloading free instructions, it is surprisingly easy to choose a custom Lego model project that after investing your money, time and effort into proves to be a costly mistake, does not live up to your expectations or is a project that you abandon.

My intention with this article is share mistakes to avoid when you are looking into buying or downloading free custom Lego model instructions from sites like: Rebrickable,, BuildBetterBricks and similar reputable Lego MOC (My Own Creation) design hosting websites.

Disclaimer: any examples I show in this post are illustrative only and are shown in-good-faith to aid in understanding – these are not shown as a critique of a designer’s work.

Mistake #1 – Buying instructions for designs that only show digital rendered images of the model

If you are considering buying instructions for a custom designed Lego model where the designer has only published digitally generated images of their model, and you cannot see photos of the real as-built-in-Lego model.  I want to you think, as spoken so aptly by the beloved Admiral Akbar:

“It’s a TRAP! “

 (…or ‘could’ be a trap, so you need to activate your Spidey senses!)

Why is this so?

Problem 1 – Digital images of a model generated from a computer Lego modelling tool like always make Lego models look amazing. The lighting is perfect, the Lego parts look perfect, and some designers add fancy glowing lights, text and other effects to make the model look highly attractive (like the example image above). 

The problem is that the real model that you will pay for and build in Lego from the instructions provided is not going to look exactly like, and likely not as good, as what you are seeing represented in the digital images.

Problem 2 – This is not always the case, it depends on the designer, but if a designer has designed their model on their computer and generated images and instructions from their computer model without building the model themselves (and publishing photos of their build).  It tells me that they may not have done real-world testing of their design and instructions. Meaning the physical Lego model may have stability issues and the instructions are likely to contain errors.

The combination of these problem means that you may put a considerable amount of money, time and effort into a custom Lego model build where:

  • The end result is disappointing as the look of the real Lego model that you build does not match-up to your expectations that were based on the digital images that you saw;
  • the model may be fragile;
  • and the building processes may be frustrating due to instruction step errors.

But Simon, I’ve found this custom Lego model design that although it has only digital rendered images published for it I still really like and want to build.  Can I make an exception?

You can in cases where you:

  • trust the designer as they have a track record of well-designed models
  • and/or you may have built one or several of their models in the past
  • and/or where you can see online, say on Rebrickable, where other builders have posted up photos of their build of the design so that you can get a sense of what the real model is going to look like.
  • You like the design that much that you are prepared to ‘roll the dice’ and deal with any issues that may arise as you work through the build.

Mistake #2 – Not checking that the cost of parts matches your budget

There’s no mistaking that custom Lego model projects are more expensive than their equivalent sized standard Lego set builds.  But the payoff for this cost (in most cases) is a much higher quality model like the UCS high-fidelity Millennium Falcon model pictured above.

The reason that custom Lego model projects are more expensive is that you have to source the parts you need for the build from BrickLink yourself; and you will likely have to place multiple seperate orders to get all of the parts that you will need to complete a project.  Each order incurs a shipping fee, and this can quickly add-up.

What I recommend doing before you even consider buying or downloading instructions for a custom Lego model design is to do a ‘sanity check’ of the parts cost, scaling the cost indicated by + 20% to give you a more realistic figure to account for shipping and parts price variability. 

Ask yourself: “Am I comfortable paying that amount for this model?”

If the answer is yes then go ahead, else consider another project!

Mistake #3 – Not checking the model design for use of rare parts

Custom Lego model designs that use a lot of older, possibly discontinued, ‘rare’ Lego parts should be avoided if possible.  The reason is that these parts will not only be expensive on BrickLink due to their rarity, they may also be hard to buy as they may only be sold by a limited number of BrickLink sellers.

Checking a design for rare parts (old parts or rare colour parts) is easy to do on Rebrickable. Just click on the Inventory tab on the Rebrickable page for the model you are interested in, rare parts will be highlighted as shown in the example above.

For other sites like or BuildBetterBricks it is not possible to do this check.  But if you are in doubt, it can be worth sending a message or email to the designer or seller of the design to ask whether the model uses rare or hard-to-find parts.

Mistake #4 – Not matching the custom model project to you level of experience

If you are new to building custom Lego model projects, I highly recommend that you ‘start small’ and only pick custom Lego models to build that have less than 500 parts.  If you have built standard Lego sets building a custom Lego model will not be an issue, the issue is that the method and process of ordering all the parts for a custom build from BrickLink is likely to be challenging for a first-timer and takes getting used to. 

Large multi-1000-part custom Lego builds involve placing multiple BrickLink part orders, may involve sourcing some parts from Lego Pick-a-Brick or even eBay, and it can take weeks, even months, to source all of the parts that you need. Going through this process for your first custom Lego model project may quickly become overwhelming.

You are best off to start small and simple, and once you have a good understanding of what’s involved then go big if you want to!

Mistake #5 – Not checking review comments or doing your homework

Before you commit to buying instructions for a custom Lego model it is always worth doing a little investigative homework to check what other people who may have built the model have to say about it.

If buying instructions from Rebrickable check the Comments tab on Rebrickable page for the model you are interested in.  Alternatively, if you are buying instructions from a site that doesn’t show review-type comments for models, do a Google search for the model in question to see if any useful information comes up on Lego forum sites like Eurobricks or even on Reddit.

If you discover that there are comments or posts about the model’s parts being very difficult to source or comments like what you see in the image above, then I recommend you consider an alternate project!

Please note however that in a similar way to reading Amazon product reviews you do have apply a ‘sense check’ to what people post or comment on for a custom Lego model. 

Sometimes the issue or problem they may be complaining about has more to do with the person posting the comment versus there being an actual issue with the model design or instructions. For example, the comment poster simply did not understand what was involved with the project as they are inexperienced with building custom Lego model projects and took on a project above their skill level.

Mistake #6 – Buying instructions that have a very high price tag

I’m talking about buying custom Lego model instructions with a price tag of over $100 USD.  In some cases for very large custom models that have been designed by proven and skilled designers a high instruction cost may be ok as the price is commensurate with the quality of the model and the work put into to creating it by the designer (example above from Mirko @ StarBricks). 

But if you see a high instruction price tag and the quality of the design or scale of model doesn’t seem to match up to the asking price for the instructions, it may be worth considering another project or contacting the designer to understand why the instruction price is so high.

Mistake #7 – Buying instructions from random ‘Lego MOC’ websites

There seem to be a worrying number of random Lego MOC websites that have appeared over the last few years that offer custom Lego model instructions of dubious quality and/or that may be selling designs without the authorisation of source designers.

If you are on one of these sites and your Spidey senses are telling you ‘this site seems dodgy’ do not make a purchase from the site.  Not only are you supporting the questionable site, if you do make a purchase, you are handing over personal and payment information that potentially could be mis-used.

I recommend you play it safe and source instructions for custom Lego projects from established, trusted and well-known sites only.

Mistake #8 – Buying ‘kits’ of custom Lego designs published on 3rd party websites

Related to mistake #7. Avoid buying ‘kits’ of custom Lego model from 3rd party sites at all costs.

I’m not talking sites/ brands like CaDa that actively partner with well-known Lego custom model designers to bring their designs to market as a ‘set’.  I’m talking about the plethora of sites that either legitimately or illegitimately advertise and sell custom Lego models as kits where they provide the instructions and non-Lego manufactured parts to you, often at a very low price.

These offerings are a double trap.  Not only are you not able to see what the real model looks like (these sites typically only publish digital rendered images and not photos of the models they offer), you also can’t see what the box, instructions and parts look like to understand the level of quality of the product offered. 

In essence you have no idea of exactly what you are paying for, so this is clear no-go.

In summary:

  • Avoid buying instructions for custom Lego models where the designer has not published photos of the physical model built in Lego.
  • Make sure you check that the cost of parts for the custom model you are interested in is acceptable to you before you go ahead with purchasing instructions and parts.
  • If possible, avoid custom Lego models that contain a lot of rare or old discontinued Lego parts.
  • If you are new to custom Lego models, start with small projects first. If you like the experience, then progressively tackle larger projects.
  • See what you can read and find out about a custom Lego model project before you commit to it. Other people’s experience with building the model you are interested in can give you valuable insight into what to expect.
  • Avoid buying custom Lego model instructions with an extremely high price tag (unless the model is by a skilled and trusted/reputable designer).
  • Do not buy custom Lego model instructions from random/questionable third party ‘Lego MOC’ websites
  • Do not buy third party ‘knock-off’ kits of custom Lego models.