Parametric French Cleat

A parametric french cleat that can be glued or screwed to other objects.

The parameters are in mm. They are:

$fn = the higher the number the smoother the hole
height = the height of the short side of the cleat
width = the width of the cleat (like the thickness of the board if it were being made of wood)
length = the length of the cleat
numholes = the number of screw holes
holeradius = the radius of the whole in the cleat
countersinkradius = the radius of the countersink