It is called rope work that the method of the more the force is applied, the more the rope knot will not be untied, and easily untying the rope knot when the force is not applied.

You will need to learn rope work in order to attach a lift bag to your recovery object or to set up a rope for search.
Be sure to learn typical rope work.

Do not do rope work on a rope that is on force, as it is dangerous if your fingers are caught in it.