Continuing my trend of bookbinding tool parts, an H key for a sewing frame. You need a few of these if you want to bind books with tape.

Ignore my previous suggestion of chipboard, it's a lot of work for a key that won't last very long. I tried quarter inch oak, but that splits too easily along the grain, I might upload some pictures later, but trust me, it doesn't work. I bought some quarter inch pine plywood, I'll see how that works when I have some time.

Either print the .stl on a 3d printer or lasercut the .dxf on a laser cutter.
Also I made a second .scad and .dxf in imperial units designed to be cut out of wood. For that one use a quarter inch drill to drill the holes, then chisel out between them. Finally cut out around the outline with whatever tool you prefer. I'm fond of a Japanese woodworking saw in conjunction with a chisel.