Trowel cap (customizable)

This is a customizable trowel cap. The default values (and the included STL) are designed to fit a trowel with a blade 38.2 mm wide by 0.6 mm thick. If customizing it's best to make the the hole slightly wider (e.g. about 2 mm) and minutely thicker (e.g. 0.05 mm) than the blade.

The large curve radii are not customizable; their radius is the same as the distance that the cap extends away from the blade (the `e` parameter).