Used to secure a rope to a pole, or to start or finish a lashing. Pass the running end of the rope over the pole twice. Then pass the running end over the standing part of rope, and tuck it back up and under itself, forming a half hitch. Repeat this for a second half hitch.
This knot has a redeeming feature - it rarely jams!

Tip. Superior to a Clove Hitch for starting and finishing a lashing as the half hitches prevent this knot from unrolling, as they have the effect of locking the knot. The Clove Hitch looks neater (!) but it has a tendency to unroll, and can be difficult to tie tightly when tying off.