Small grommets are also called eyelets, especially when used in clothing or crafting. Ferrules are also often referred to as eyelets or grommets within the manufacturing industry. Sails feature reinforcements of fabric layers where lines attach at grommets or cringles. Rubber, plastic or plastic coated metal grommets are used to avoid this. Mated rubber grommets provide a positive seal. Low Pressure Molding is also used for sealing connectors and molding grommets and strain reliefs. A wire hook that engaged grommets on the cartridge belt replaced the belt-hanger. Grommets may be aluminum, stainless steel, or other materials. Tight fitting rubber grommets can also prevent the entry of dirt, air, water, etc. Grommets in electrical applications are referred to as "insulating bushings". Rubber grommets help protect the paint on the doors and the jack points. Square sails and gaff-rigged sails also have grommets at corners. Open grommets are placed near the top for ventilation. Grommets for hanging are attached and the blocks are numbered and photographed. A sail may have "reef points," small holes in the sail between the grommets.