A question-----I am sure, quite basic for many of you-----are all rail attachment systems for AR's of the type that must be "pinned" on or some attached/detatchable similar to removing a standard handguard. Thanks!  CBR

FAQ: The Big Thread On FF & Railed Forends

2 piece rail systems work like standard handguards and Free Float tubes are "pinned on" (not the correct word)

There are two types of rail attatchments for the AR. The 2 piece rails and the free float (FF) type.

The 2 piece rails attaches like the regular handguards. They make use of the delta ring and handguard cap to "hold" them in place. There are some other 2 piece HGs that have additional screws on them that clamp both pieces together. ex. Surefire.

FF rails are one piece. One solid cylinder with rails on the 12, 3, 6 and 9 o'clock. These are fastened on the upper reciever where the barrel nut usually goes. You have to remove the front sight base in order to slip this on the barrel.