Nipple pin prevents slipping within the channel. Place a 1/16" drill bit into the drill guide hole within the nipple.
Symmetrically align the insert in the feed slot. Strike the drill bit to cause a detent in the aluminum back web.
Remove the insert and drill bit. Use 1/16" dit to drill a guide hole. Then use 1/8" bit and finish with 3/6" bit.
Hand twist a larger drill bit to remove any burrs.
A large tweezer is handy for removing the insert. Squeez & pull out insert.
nylon surface can be dyed a color. Black is best for added UV blocking.