During preparation for pressure test of BOP, Asst. Driller was lowering the traveling block with elevator by releasing the brakes. While doing so, the AD raised the brake handle lever which got stuck onto the driller console. As the traveling block lowered, AD tried to pull the brake handle lever, but by that time, the traveling block impacted on the rig floor handrail. No injury to personnel , no damages observed on the traveling block, rig floor or elevator.