This is an improved live mouse trap that I designed and built after seeing the concept drawing at the bottom of this page. Within 5 minutes of setting this trap I caught my first mouse. Less than 5 minutes after resetting the trap I caught the second. Sorry for the lack of pictures for the build process. It went so fast I forgot to take pictures.

Step 1: Materials and Tools

This was all stuff I found lying around the house.

Materials

wire grate
wide tomato can
kite string
mouse trap (the classic kind)
Duct/Electrical tape
U-shaped bolt
1 1/2" straight thing (I used a thicker metal wire)
thin-flexible metal wire
Some small bolts

Tools

Drill
Drill bits for metal
Wire cutters
Scissors

Step 2: Build Instructions

Cut the wire grate into a square measuring 1 inch larger than the diameter of the can.
Center the can on top of the grate.
Fold one edge of the grate up (or down) completely so it's flat on itself.
Fold the other 3 edges up so they are perpendicular to the flat part of the grate (make a 3-sided box). This box should cup the open end of the can with about a 1/2 inch overlap on 3 sides.
Drill one or two small holes near the open end of the can (against the edge almost) about 1/2 inch apart.
Use the flexible wire to attach the double-layered side of the grate to the can, creating a hinged lid.
Tape/Make safer the exposed edges of the wire grate.
Using the U-bolt as a guide, drill two holes on the opposite edge of the can from your "hinge" you just made.
Place the U-bolt into these holes with the closed (the bottom of the U) inside the can and the nuts on the outside.
Drill a hole in the bottom center of the can.
Drill a hole in the center of the mouse trap (only the wood, don't drill something else)
Attach the mouse-trap to the bottom of the can through the hole you just drilled with a bolt.
With the trap disarmed and the trigger (the part for the bait) closest to the ground, drill holes through the wood of the trap and the can at the top edge (centered) next to the spring bar and next to the trigger.
Using your thicker wire or whatever you found, solidly attach it to the trigger and through the new hole into the can. This will now be the thing that holds your bait.
Tie your string onto the center or top of the grate, run it through the U-bolt, and out the bottom of the can. Loop it around the spring bar and bring it back to the U-bolt and tie it there. This will make your trap hold much tighter.
Set the trap, and place bait on the inner trigger. You're done.