Building up my Cannondale Six13, realized the cable guide under the bottom bracket is missing.

I went and purchased a purple cable guide, and seperately, they gave me a screw and a washer-like thing. I don't understand how to install this thing.

I looked at my other bikes and they all seem to have a threaded hole at the bottom of the BB to screw the cable guide into. My Six13 just has a hole (threadless.) With this being as it is, how do I attach my cable guide to my bike?

(My only idea is some kind of glue, but I'm sure there's some real way to do it.) How does this work?

I've seen bikes with only one hole for the cable guide (no water drain hole?) and no threads in the hole. Some brands provide a self-tapping screw that is meant to be screwed directly into the hole. I much prefer to drill the hole to the proper size (if needed) and thread with an M5 tap, to use a common M5 stainless steel bolt. Obviously the bolt must be quite short and installed before the BB, to insure it's not too long and contacting the BB.

If you bought the frame from a LBS, you should take it back and let them provide and install the missing part.

Alternatively, you can install the guide without a screw. There should be a circular 'nub' where the screw goes on the gide that will fit into the hole on the frame. It's a bit cumbersome during set-up, but the pressure of the cables holds the guide tight to the frame. I had a bike that I did this on because of the screw interfering with the bb sleeve and rode it that way for years, no problems.

If you are really anal you can stick it on with double sided tape or silicone sealant in the absence of the screw. Just make sure whatever you use is removable as I have seen those guides wear out occassionally and need replacing.

I've seen bikes with only one hole for the cable guide (no water drain hole?) and no threads in the hole. Some brands provide a self-tapping screw that is meant to be screwed directly into the hole. I much prefer to drill the hole to the proper size (if needed) and thread with an M5 tap, to use a common M5 stainless steel bolt. Obviously the bolt must be quite short and installed before the BB, to insure it's not too long and contacting the BB.

If you bought the frame from a LBS, you should take it back and let them provide and install the missing part.

I agree, the best plan is to tap the hole and use a threaded bolt. One, it can be removed to drain water after wet rides, and two, it can be removed to have another cable guide installed if the original gets worn down over time.