How to Make a DP Trap

Place the 6-inch piece of tubular steel in a steel vise, horizontally. Use a T-square and permanent marker to measure and mark a line all the way around the right end of the tube, 3/4-inch from the end. Use a power hacksaw to cut down the line but not through the bottom side.

Rotate the piece 90 degrees to the left and cut out a three-sided section, leaving only one flange -- what was originally the bottom flange -- on the right. Use a hammer to bend the flange 90 degrees to the right so it is perpendicular to the long axis of the piece. Measure and drill a 1/4-inch hole in the center of the 3/4-inch flange and round the points off the corners.

Place a 1-by-5-inch 90-degree torsion spring on a flat work surface, with the short arm pointing vertically and the long arm flat on the surface and pointing away and directly ahead. With this alignment, place the spring in the vise and make a right-angle bend to the left at 1 inch from the end of the long arm, pounding it with a hammer. Repeat this process with the other spring, making the right-angle bend to the right.

Weld the bent arms of the two springs together so that the springs are side-by-side with the bent arms overlapping.

Place the tube in the vise with the long axis vertical and the bent flange at the bottom, facing backward. This surface is the top side of the trap. Measure and drill two 3/16-inch holes, one in each bottom corner of the facing side, adjacent to the curve of the bent flange and 1/4-inch from either edge. Do not drill through the other side below these holes.

Measure and drill a 1/2-inch hole through both the top and bottom sides of the piece, at 1 inch from its top, vertical end. Measure and drill two overlapping (side-by-side) 3/8-inch holes through the top surface of the facing flange, at 2 inches down from the upper end of the piece. Use a small file to straighten out the combined holes to form a single rectangular hole 3/8-by-3/4-inches to form the trigger slot. Drill a hole through both sides of the piece, horizontally, at a point that will cause the hole to intersect with the trigger slot.

Measure and cut a 2-inch piece of 1/8-inch steel rod. Place it in the vise and heat its midsection until it is red hot. Use a pair of heavy pliers to wrap the piece of rod around a narrow-shaft screwdriver, producing a 1 1/4-inch piece with a 360-degree loop at its midpoint. Heat and bend a 90-degree angle in one end of the piece, in the same plane as that of the loop, 1/2-inch from its end.

Pound the tip of the 1/2-inch flange flat. Cut a 1 1/4-inch straight piece of 1/8-inch steel rod. Slide the looped piece -- the trigger pin -- down into the trigger slot and insert the small, straight piece of rod through a side hole, then through the loop and then out the other side hole. Lay the piece down on top the vise and pound the exposed ends of the 1/8-inch straight rod into a double-sided rivet.

Slide a 20-penny nail through the hole in the vertical flange at the back of the trap top -- pointing toward the trigger slot. Measure the exact distance down the nail, to the inside of the 90-degree bend in the trigger pin. Remove the nail and cut it to fit this length. Pound its end horizontally flat. Return it through the hole and ensure it reaches the trigger pin correctly. Weld a dot of steel on the nail shaft to keep the nail attached to the tube.

Measure and cut a 1/8-inch piece of steel rod for the strangle bar. Make two right-angle bends in it, forming a U-shape with arms 2 1/4 inches long. Insert the ends of the arms up through the interior of the tube and out the two 3/16-inch holes near the vertical flange. Bend the ends toward each other at 90 degrees and weld their surfaces together.

Weld the two torsion springs onto the top of the trap where their combined flanges extend exactly over the combined arms of the strangle bar. Use a twist clamp to draw the combined arms of the springs down to meet the combined arms of the strangle bar and weld them together. Place a 1/-2-inch machine bolt through the 1/2-inch hole in the piece to block off that end. Weld a small steel chain to the side of the trap to secure it to a tree.