Originated by Clifford W Ashley, author of the famous Ashley Book of Knots, the Constrictor can well be used as a temporary whipping or seizing. It may also serve to tie the neck of a sailbag or kit bag, but in this case a slipped version might be desirable to make eventual undoing easier.
The essence of the knot is that it becomes ever tighter as tension is applied to the ends without loosening as the strain is taken off them.
To form the knot, take a Round Turn with the working end crossing the standing part (like the beginning of a Rolling Hitch) and make an overhand knot beneath the crossover point using the working end and the standing part. This process should be made clear by the diagrams. Then pull as tight as required. For easier untying, form a slipped overhand knot using a bight in the working end.