Yup, this trap works! You can reuse your old, bent, wire coat hangers and go crabbing! The one in the photo was undersize, though, so he just posed for a picture and went back home. Because I didn't think to post this at first, I have drawn diagrams for the instructions.

Supplies

Materials:

3 wire coat hangers
2 clothespins
gardening wire
waterproof tape
superglue
50 m (164 ft) strong cord/rope (3 mm thick)
10 m (32 ft) plastic cord or string (1.5 mm thick)
12 cm (4.5 in) diameter plastic lid (from a peanut butter jar, etc.)

Tools:

scissors
pliers

Step 1:

Remove the springs from the two clothes pins. Weaker springs with a larger loop work best (I got mine from cheap, plastic, dollar store clothes pins). Use pliers to straighten out the legs. Then, bend one of the legs back so the two legs point in opposite directions.

Step 2:

Use pliers to unwind the top of the coat hanger.

Step 3:

Thread the wire hanger through the hole in the spring, and then repeat for the second spring. Move the springs to the opposite corners of the coat hanger. Afterwards, use the pliers to twist the opening in the coat hanger back together.

Step 4:

Take the second coat hanger and untwist the top. Bend the coat hanger into an open rectangular shape and cut off around 4 cm (1.5 in) of the curved end. Repeat with the third coat hanger.

Step 5:

Take the second coat hanger and use pliers to bend the ends twice around the first coat hanger. Make sure they are on the outside of the springs. Then, attach the third coat hanger to the first one in the same way, this time making sure that it is on the inside of the springs.

Step 6:

Line up the legs of the spring with second and third coat hangers, and use gardening wire to tightly wrap them together. Repeat for the other spring. Cover with waterproof tape.

Step 7:

Using pliers, bend the hook of the first coat hanger into a loop and secure with a twist. Add some tape for extra safety.

Step 8:

Cut an 80 cm (31 in) length of 3mm thick rope and tie it to the middle of the second coat hanger. You can use a Blake's hitch (https://www.netknots.com/rope_knots/blakes-hitch) or any other secure knot. I used superglue to seal the ends of the rope and to glue the hitch together (so I didn't use a stopper knot). Thread the other end of the rope through the loop of the first coat hanger, up, around, and back though the loop. Tie the rope to the middle of the third coat hanger so that there is just enough rope for the first coat hanger to stand vertically and the other two to lie flat on the floor.

Step 9:

Reserve around 80 cm (31 in) of the 3 mm thick rope, and tie the rest to the loop made by the string in the previous step.

Step 10:

Take the plastic lid and cut the rim off so that it is a flat circle. Make holes 5 mm (3/16 in) in diameter where the red Xs are in the diagram (if you don't have sharp-tipped scissors, you might need an electric drill).

Step 11:

Use gardening wire to tie the plastic lid to the first coat hanger.

Step 12:

Divide the 80 cm (31 in) of rope into four pieces. Take one piece and string it though the top right of the holes in the centre. Insert it back through the hole directly under it. Repeat with the left side, turn the trap around, and repeat with the other side. These are used to secure bait to the trap.

Step 13:

Cut 10 strips of 1 m (39 in) long 1.5 mm string. Tie the halfway point to the coat hanger on one end: the overhand knot/bend works well (https://www.netknots.com/rope_knots/overhand-bend...). Repeat for the rest of the string and space out evenly on this end of the trap. You can use superglue to secure the positions of the knots. Note: the illustration only has four pieces of string instead of ten. Starting at the left or right side, tie one leg of the string to the side of the coat hanger. Take the other leg and tie it to one of the legs of the adjacent string (you can use the overhand bend). Finish the row in the same way, and continue tying rows until you reach the end of the opposite coat hanger. Tie the strings to this end and secure with superglue.

Step 14: You're Done!

Congrats! If the springs that you have are too stiff and it takes a significant force to close the trap, you can disconnect the spring on one side, or modify them by enlarging and loosening the coils. Have fun crabbing!