The construction of rock-climbing anchors requires careful practice and attention to detail. The slings found on an anchor of improper length might undergo excess force or become offset, putting too much force on one side. The best climbing anchors consist of equally spaced rock-climbing slings that meet at a single point. Equally spaced slings apply an equal amount of force to each part of the anchor, creating a safe system.
Wrap a circular sling over itself to create a doubled sling that is half the length of the original. Fold the sling again to shorten it to a quarter of its original length. Each fold reduces the sling's length by about 50 per cent.
Twist the sling. Hold one end of the sling and twist from the end. The twists become tighter and tighter, effectively shortening the length of the sling.
Wrap the end of the sling around the anchor carabiner multiple times. Each wrap around the carabiner shortens the sling by just less than the circumference of the carabiner -- usually about an inch.
Tie an overhand knot in the rock sling. An overhand knot shortens the sling by a few inches, but decreases the strength of the sling.
Only cut the sling as a last resort. Cut, frayed, or otherwise damaged slings must not be used in a rock climbing anchor.