You misunderstood.The laser is only to get your crossbow sighted in,not to hunt with.
The one I included screws into your arrow/bolt in place of the field point or broadhead. You cock your crossbow, set the arrow , put the crossbow on a rest and the laser shines on your target.
You then look thru your scope or what ever sight you are using and adjust it so it centers on the laser light on your target. Same as the last paragraph in your reply. There is no clamping or a fixing to the rail since it becomes the point of your arrow.
I thought I would offer the tip since I found mine so useful when setting up my crossbow
