threaded holes in riser??
 

i was looking over my horton tacoma xbow today, was going to shoot but its raining so gonna try tomorrow. while i was installing the foot stirrup i noticed two other holes, they are threaded but no screws came in them like the foot stirrup holes did. if you look thru the holes, they line up with the bolt that mounts the riser to the rail. i can see the threads of the bolt in one hole in the other i see the part of the rail the riser goes on. what are these holes for?, the only thing i can come up with is that a person could put set screws in them to help the riser stay tighter to the stock assembly because of recoil. thanks for the help, i'm new to crossbows so i don't know much yet. thanks again.

i finally got some pics, mabe this will help tell what they are. thanks