The holder consists of a two-legged block (2) which is joined to the baseplate (1) and fitted with off-centre pivotal holding clamps (3) and a sidewall. The automatic holding action derives from the design and siting of the clamp. The block and baseplate form the main component whose opening (13) opens downwards when the plate is vertical and which has radiused outlet edges (12). The opening leads up vertically into the block and slopes at thirty-five deg. into the leading leg (5) and at ten deg. into the rear leg (6) level with the first tooth (11) of the clamp with the result that the opening is three to four times wider in the upper part of the block than in the clamp region.
