The knot prevents the end of the rope from slipping through a fastening or loop in another rope or from unreeving when reeved through blocks. It is easy to untie. It also makes a desirable knot to prevent the end of the rope from slipping through small openings, as when rope handles are used on boxes. Notice that in the wall knot the ends come up through the bights, causing the strands to lead forward. In a crown knot, the ends go down through the bights and point backward.
Single sheet bend.
Double sheet bend. Note that in the square knot, the end and standing part of one rope comes out on the same side of the bight formed by the other rope. The square knot will not hold if the ropes are wet or if they are of different sizes. It tightens under strain but can be untied by grasping the ends of the two bights and pulling the knot apart. Tying a rope to an eye.