One of the things I've learned to do in my prints, when I have two parts that will be joined together, is create a directional key and matching key holes in each part. The holes should be half the depth of the key. The key and holes should fit together in one direction only. I can't count the number of times I've glued two parts together that were slightly askew, or backwards, or...

CAD drawing of key and parts with key holes
photo of finished parts


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