Support a wooden dowel across a doorway about 3 feet high using a string tied tightly to one end (B) and supported from a door hinge. Support the other end of the dowel with an ice timer (A) and string (E). I use an adjustable clamp, but a couple pieces of duct tape would probably work in a pinch. Tie your special ring device (C) to a cord with a loop tied in the other end -- the loop must be significantly larger than the diameter of the dowel. Slide the loop onto the dowel as close to the hinge side of the stick as possible (B) and attach whatever you want to restrain to the Ring Device (C). Pull as hard as you want -- it's not coming loose.
When the ice melts, the end of the dowel will drop and swing toward you, and the loop will slide off the dowel.
A few things to consider:
1. Don't make the dowel so long that when it drops it still doesn't clear the door jamb -- about 4 inches longer than the door width is all you need.
2. Make sure that the ice timer string is arranged such that it won't get tangled when the weight drops. Arranging the string in a wide V shape will keep the weight from hitting the dowel.
3. Don't put anything delicate or breakable (like your head) too close to the dowel because it can swing wide with some force, depending on how hard you're pulling on it.
