Built from nothing but scrap plywood and spare or recycled hardware for completely free, or you could build it for really cheap if you had to buy anything

With an "industrious" back yard and a large vacant field behind the neighbors across the street we occasionally find an opossum nesting somewhere we can usually catch with a gloved hand. Yesterday I spotted a juvenile running across the street, I gave chase but it hid in the neighbors garage and I lost track of it after a few minutes.

Figured it mustn't be difficult or complicated and came up with this after having seen a couple of other traps before.

Step 1: Tools and Supplies

You will need the following supplies:
1/2" plywood
1/2" x 1/2" strip
4 hinges
2 small washers
Bailing wire / metal hanger
Screws
Twine / String

You will need the following tools:
Saw
Drill / Driver
Tape Measure
Square
Side Cutters
Razor Blade
Pencil
Drill bit
*optional* A radio to jam out to

Step 2: Measure and Cut

Measure, layout and cut the following pieces of plywood:
(1) 12" x 48" for the base
(3) 12" x 40" for the walls and ceiling
(2) 10 7/8" x 11 3/4" for the doors
(2) 3" x 10" for the locks
(2) 5" x 10" for the triggers

and cut the 1/2" x 1/2" strip into:
(4) 3"L for the door jams
(2) 6"L for the lock plates

Step 3: Assemble the Doors

(do this step twice, once for each door)
Attach one end of a hinge to the lock,
Center the lock side to side and 1 1/2" in from the 11 3/4" side of the door,
Attach another hinge to the other 11 3/4" side on the back or edge that will
allow the door to be both open and closed without binding the hinge.
See note in step 5 picture in comparison to the one above.

Step 4: Build the Body

Screw the walls to the ceiling (assemble upside down).

Step 5: Attach the Doors

(do this step twice, once for each door)
Line up the door with the lock right next to the ceiling and attach the door hinge,

then, holding the door in what will be the closed position attach the door jams.

Step 6: Attach the Base

Attach the base so that the walls are centered.

Step 7: Space and Install the Lock Plate

(do this step twice, once for each door)
Check that the doors swing freely without binding against the walls or base, if you used a larger
hinge then you may need to shave a little more off the door.

With the door in the closed position lift up the lock and set the lock plate next to the door,
then slowly pulling the door open find the point at which the door swings without moving
the lock plate then pull the lock plate another 1/4" - 3/8" further away and screw to the base.

Step 8: Making the Sear

(some parts of this step * require you to do them twice,
once for each door)

Drill a hole in the middle of the ceiling, then using the
drill bit as an anvil bend the wire around it to make a loop.
If your using a coat hanger it's a lot stiffer and you'll need
to use the cutters or a pair of pliers to bend.

*Loosen one of the screws on the lock hinge and tie the twine
around it and re-tighten the screw, run the twine behind the lock.

*Prop the door so that it is about a 1/2" from all the way up and
tie the other end of the twine to the washer at the length needed
to line the washer up with the hole.

Stick the sear in the hole from the inside and put the washers around
it and let the weight of the doors hold the sear in place. Make sure the sear
is all the way against the ceiling and that the washers are all the way down in
their natural resting position and trim the wire so that there is an extra 3/8"
over the washers.

Step 9: Making the Trigger

Set the two trigger boards on top of each other and drill a hole through
both boards about an 1/4" in from the edge centered from side to side.

Then tie a semi-loose loop through the two holes so that the
triggers can hinge freely yet still pull immediately on the twine.

Tie the other end of the twine to the loop in the sear at the length
needed so that the top of the sear clears the top of the ceiling
when the triggers still have another 1/8" of travel down. This
roughly equates to the trigger plates being a 1/2" off the base at
the underside of the peak.

Try to keep the triggers low as best you can, if they are too high
then they will be too steep of an angle and will reduce the sensitivity
of the trigger, the lower they are the more sensitive the trap will be.

Step 10: Adjusting the Sear

Now that the weight of the triggers are helping to pull down the sear we need to adjust the pull weight.
While holding the sear up with your hand set the washers into place and using your thumb gently push
on the sear in the opposite direction of the top washer until the trap stays set, if your using a coat
hanger it's a lot stiffer and you'll need to use the cutters or a pair of pliers to bend. You're not trying to
put a hard bend in it just a slight arc to help overcome the weight of the triggers. Bend it too much and
the weight of your prey may not activate the trap, the less you can bend it the more sensitive the trap will be.

Place some bait (dry cat food) on either side of the peak of the triggers right next to the twine and a
little on either side of it just inside the door jams to entice the animal to walk further in and through
for a better chance of attracting and trapping.

Step 11: How It Locks/unlocks

When the animal steps on the triggers his weight pulls the sear down releasing the washers and doors.
When the doors fall the lock slips over the lock plate and falls down into the locked position behind the
lock plate preventing the door from being opened from the inside.

To unlock the door simply lift up on the lock and using it as a handle lift the door open, slowly if you
think you caught something.

Other ideas:
-You could also drill a bunch of small - medium holes or cut a big square out and staple wire mesh in a
wall so you can see what's inside.

-Put a handle on top to carry the box and animal to your release area.

The first night I set it out I caught the neighbors cat, this thing works.

Step 12: Update

**UPDATE** **6-18-13**

I've had the trap for a few weeks now, the one I was chasing after was found dead from one of the neighborhood cats or the neighbors dog a few days after posting the instructable.

Knowing that opossum have an average of 6-10 babies per litter I've kept the trap running and this is the 2nd little guy I've caught with it.