All known exits to the warren are netted. The bolting rabbit will run into the net, pursing up the net. Care is taken to remove snags that might impede the operation of the net.
The net pegs are made from oak and painted with fluorescent paint. Fred prefers spun nylon cord for the net, the net rings are one piece. Some people have a preference for using hemp cord, but they must not be allowed to be stored while damp, as they will rot.
 Fred thoughtfully sets out the nets.  To see a ferret entering a burrow.

You can see in the right hand  picture how the net is set about the bolt hole. The rabbit will run into the net and upon the section of net laid in the hole, thus drawing the cord about entry of the net, pursing up the the net, and trapping the rabbit. The peg is normally pushed into the soil, but can be wedged in a root or the the cord wrapped about an object.
Picture of Ferret entering a burrow.

Purse nets.