AR15 flattop mount question

[majormarine]

if you look at the following picture:

what is the roll pin (left side in the picture) at the bottom of the mount for?

can i take it out and the mount still works fine?

Thanks!

 

[toya]

The pin should sit in one of the picatinny notches. Thats how the mount stays put and doesn't move on the rail.

 

[Artiz]

^^ What he said.