Purchase a flash bang. Select or hold the flash bang then go to a corner wall. Push or walk against that corner until u can't go further then throw the Flash bang grenade. The Flash bang grenade won't bounce off, instead, the wall would magically absorb the grenade. As the Flash bang explodes, the blindling light would affect anyone within 20-30 meters as if blinded point blank from the flash bang explosion. No need to throw at doors or openings !