can you sleep on a bed of nails
A bed of nails is an oblong piece of wood, the size of a bed, with nails pointing upwards out of it. It appears to the spectator that anyone lying on this ``bed'' would be injured by the nails, but this is not so. Assuming the nails are numerous enough, the weight is distributed among them so that the pressure exerted by each nail is not enough to puncture the person's skin.
Bed of nails