Full answer
A stripped screw is one where the driver slots have been worn smooth, so the screwdriver spins without catching. The rubber band trick works on mild to moderate stripping: the rubber material fills the damaged grooves and gives the driver something to bite. Use a wide, flat rubber band, press down hard while turning counterclockwise slowly.
If the rubber band method doesn't grip enough, try a manual screw extractor. These are inexpensive drill bit sets that have reversed spiral flutes — they dig into the screw head as you turn counterclockwise, biting harder as they go. Drill a small pilot hole first if the screw is deeply stripped, then insert the extractor and turn with a T-handle or low-speed drill.
For screws with enough head above the surface, locking pliers (Vise-Grips) clamped tightly to the screw head give you the most torque of any method. Clamp as close to the wood surface as possible and rotate slowly. This method rarely fails when there's accessible head material to grip.
When the screw head is fully below the surface, cutting a new slot with a Dremel or rotary tool lets you use a flathead screwdriver in the fresh channel. Make the cut at least 2mm deep for adequate driver engagement. For critically stripped screws embedded in wood, drilling out the screw entirely and using a wood filler plug is often the cleanest permanent solution.