These grey door wedges are made from either rubber or flexible plastic. They normally slipped under the door to hold it open. They prevent the door accidentally closing when unrestricted access is required.
Brass Door Bolt 50, 63,75 &100MM
Castor Cups with Felt Protector Pads Brown Small 53mm - Pack 4
Flexible Spring & Rubber Doorstops
Magnetic Cupboard Catch, 42 & 62mm, White & Brown