To build a crayfish trap, fold one piece of hardware cloth into a cylinder and two additional pieces into funnels, attach the funnels to the ends of the cylinders so that the points face one another, and finally cut an opening in the cylinder to make a door. To use the trap, bait it with chunks of hot dog or fish, and place it in a body of water where crayfish live.
Measure out a 20 by 24-inch piece of hardware cloth for the cylinder, and cut it out with wire cutters. Form the funnels out of 12-inch diameter semi-circles of hardware cloth. Bend one of the semi-circles into a cone shape, leaving a 2-inch wide opening at the top. Join the ends together with wire. Repeat this process with the second semi-circle.
Place one cone into each end of the cylinder so that the ends of the cones are flush with the ends of the cylinder. Using wire cutters, cut a 4- by 4-inch door into the cylinder. On one side of the door, loop two pieces of wire through the hardware cloth and use them to attach the loose 4- by 4-inch piece to that side. This acts as a hinge for the door. Loop string through the opening on the other side of the opening to attach the door.
Secure the trap to the bank with a length of rope. Use the rope to reel in the trap once you have caught your crayfish.