The sliding X is a two legged anchor which consists of a sling with two limiting knots (overhand or figure-8). The limiting knots are important to improve redundancy and limit extension in case one leg of the anchor fails. In the middle of the anchor, the master point is created by twisting one of the two strands 180 degrees and clipping through the "X". The twist is important to contain the carabiner if one leg fails. It has some ability to self equalize between the two limiting knots. The two limiting knots should be as close as possible to the middle without restricting the ability to self equalize, in order to limit extension in case one of the legs fails. As always, the angle between the two legs should be less than 60 degrees to reduce forces on each piece.
Each leg should use locking biners if you are top roping, but non-lockers are fine if you are belaying at the anchor. The top rope master point should always use two locked and opposed carabiners.
