The breast collar was usually reserved for horses injured by their collars in order to keep them active. To place a horse down into the bottom of the pit it was necessary to suspend it vertically with its limbs tied up and fettered. The "covered" technique of net lowering immobilised the animal in a large dark coat so that it could not see anything and remained calm during the manoeuvre. At times, the horses were simply covered with a descent mask specifically created for this purpose.