This method totally immobilizes a person on a bed without attaching the person to the bed.
1. Get a sheet of ¾ inch plywood.
2. Have the person lie down on it with arms and legs outstretched in the desired position of immobilization.
3. Trace the outline of the person’s body on the plywood.
4. Cut out the outline with a saw, sand it, and paint it.
5. Put the plywood piece on the bed.
6. Put ropes, strips of tape, or preferably leather belts or restraints at various points under the plywood piece.
7. Have the person lie on the plywood piece, face up or face down.
8. Secure the restraints, tie the ropes, or tape the tape securely to bind the person tightly to the plywood piece.
For absolute immobility, secure all these body points: ankles, calves just below the knee, thighs just above the knee, thighs just below the crotch, hips, waist, chest (not too tight), arms just below the shoulders, arms just above the elbow, arms just below the elbow, wrists, neck (if desired and using a collar with rings), and forehead, (or the rings of a head harness with bondage rings.)
If you make the arms longer than actual length, and drill holes in their ends, you can bind the person to the plywood, and hang the person up on a wall. Fun!