Railway TB/T2942-B Brake Shoe Holder Are used on  Trains to hold the brake block to enable deceleration, control acceleration (downhill) or to keep them standing when parked. while the basic principle is familiar from road vehicle usage, operational features are more complex because of the need to control multiple linked carriages and to be effective on vehicles left without a Prime mover. Clasp brakes are one type of brakes historically used on trains.