In order to learn how to build lobster traps, one must first learn how lobsters can be baited. Because lobsters are carnivorous meat eaters, lobstermen usually use pieces of fish as bait--typically mackerel or herring--for catching lobsters. The smell of the meat lures the lobster into the trap. Buy the bait from a fish processing plant.
Build the wire cage. Get wire mesh at a hardware store or home goods store. The mesh usually comes in rolls so you need to put them on a straightener first. Cut the wire mesh to build a cage that is 1.2 metres (48 inches) long by 45 cm (18 inches) wide by 38 cm (15 inches) high. You will need to cut the mesh in pieces, one each for the base, sides and top. The parts must be cut in the sizes to build a cage in the chosen dimensions. Either weld the pieces together or put them together using a clipping tool. You can also tie them together by twisting metal wires.
Make the top door. Cut a hole at the top of the cage and make a door. This will allow you to get to the trapped lobsters. You can use the mesh you just cut and reattach it to the cage by tying it with a nylon cord or a metal wire. Be sure that you close this door when you lower your trap in the water.
Make the cage rigid and strong. Attach a bridge at the top of the cage to give it strength and rigidity. Also attach one bridge for each side. You can make the bridge by using a wire mesh panel that is four squares wide. You should fold the panel four times to form a square. You can then attach it to to the cage using a metal clip or wire.
Make a brick cage using wire mesh. Put the paver brick inside. Attach it to the middle of the base using a metal wire or clips. This will serve as the weight and it will also ensure that the top of the cage is always up when it lands on the sea bed.
Create the trap entrance. Make funnel using chicken wire. Be sure that the hole is big enough to allow the lobster to fit in. Cut a hole at the side of the cage. This is where you will attach the funnel. The entrance hole should touch the base of the cage to allow the lobster to crawl in. The second hole should be up at about the middle of the cage so that the prey cannot climb back out. Cut a 65 mm (3/8 inch) by 38 mm (1.5 inch) escape panel at the side of the cage. This will allow small lobsters to escape.
Bait the bag. For the bait, you can make a small net bag. You can either tie it on the middle bottom of the cage or you can tie at the top of the cage.
Attach the marker. Attach one end of the rope to the cage. You should tie the rope in a way that the cage would not lose its balance when you hoist it up. Attach the other end to the foam buoy. Make sure that your identification number is written on the buoy. This helps identify the owner of the trap. It is also recommended that you use a coloured buoy so that you can quickly spot your own trap.
Always check with local marine authorities regarding lobster fishing policies.