If you design things (especially things like limit switch mounting) to be adjustable, it makes it possible to "Dial it in" to whatever position is needed to achieve as near perfect as is possible. It seems that no matter how precise the build, there are always those one or two things that just aren't quite right. Designing critical components to be adjustable with things like threaded jack screw holes, and/or slots for mounting bolts can make life much easier. (As opposed to disassembling, cutting, grinding, filing, sanding, etc.- which is usually the alternative when adjustability of the design is not utilized during the design phase). This important tid bit is usually learned at the School of Hard Knocks (experience).