Like my previous tripwire instructable but from items found around the office.
Step 1: Tools and Stuff, You Will Need...
Foil (from your sandwichs perhaps)
Device you want to turn on.
Step 2: Constructing the Switch.
Cut off a bit of card big enough to fill the jaws of the clip once folded in half and then some. You don't want the croc clips touching the metal bulldog clip as that would be rubbish.
Fold it in half
Take the foil (I folded it in half for strength but a strip of tape would work better) and attach to one half of the card with blutac or double sided tape. Try to place it so that it receives the mostr pressure from the bulldog clip. the metal needs to be exposed. leave enough hanging out the side to attach the croc clips to. Repeat on the other side, making sure that when folded, the touch and that the overhang is on the other side.
Step 3: Making the Anchor Line
You need to make an anchor line. Don't add the string to the clip. it'll probably just cause the guts to get pulled out when it gets tripped.
Make a loop around your card and insert that into the clip. That should hold it all together a lot better.
Step 4: The Trip Mech
Add hole to card.
Tie string through hole (the longer trip wire string)
Make sure card is wide enough to prevent any shorts within the trip switch.
Step 5: And Finally...
Clamp the trip mech in between the foiled card with the bulldog clip. Tie off the anchor securely and the trip wire securely across the path you want to arm.
Croc clips attach to the foil pads and from there, to anything you want. I don't recomed the Quick and dirty Squib for inside use but the choice is yours.