BT34 2.05" rail BT34 2.05" rail Click to enlarge The new BT34 2.05" 1913 Rail has a center to center spacing of 1.6". Two Button head machine screws can be used (not included, see BT1517) to attach this rail to the forearm of standard rifle stocks. The BT34 can also be attached to a horizontal surface on the Butt section to attach our Precision Rail Monopods.