Not only are they almost impossible to sharpen, but blade replacements are usually under $2 each, so they are treated as disposable. Some cheap hand saws for wood can also be a problem.

in the case of a hand saw, along the blade plate. A dado blade is a specialty blade used to create wide grooves in wood for shelving, door panels, inlays, and drawers. Whereas other saw blades ...

hand-cut aluminium alloy plate, nary a CNC tool in sight. The only unusual component is the saw blade itself, which might be a bit tricky to track down if you were so inclined to reproduce the build.