Catalina 22, TD17mm 6-1/8"

The WHITE nylon has a textured surface that will accept a color dye.
The BLACK nylon is dyed at the factory for the increased cost.  (Black is better for blocking UV)

Nipple DRILLING INSTALLATION:
The insert sleeve is symmetrical, with a bottom nipple pin. 
Insert a #55 drill bit (or 1/16" bit) into the nipple's drill guide hole and center the insert into the feed slot.
Make sure the nylon insert is centered within the feed slot.
Lightly hammer the drill bit to make a mark into the aluminum of the back web. 
Remove the insert, then center punch the location.  First, use 1/8" drill bits, then finish drilling holes with a 3/16" drill bit.  Hand twist a larger drill bit in the holes to remove any burrs.
The nipple pin of the nylon insert will key into the holes to prevent unintentional sliding of the insert. 

Catalina-22-TD17.12 pg757B 155