Rep Power: 0

What exactly holds them in place? Are there clips that kind of act like drywall screws?

 
Rep Power: 304

i too would like to know. i know someone that got their sidemarkers jacked.

 
Rep Power: 321

They are held on to your fender by clips.
The clips are on the sidemarker itself.
The sidemarker is plastic but the clip is metal.
If installed properly they should hold pretty tight.
But of course any idiot can pull it off if he/she pulled hard enough.

 
Rep Power: 812

My holes were too big for the clip to work, so I just used silicone. Holds perfectly.