Rubber gaskets are elastic components used for mechanically sealing the microscopic gap between two mating surfaces or joints. Examples of these surfaces are flange faces of piping and fittings, mating surfaces of an automotive cylinder head and engine block, tank rims and covers, door edges, frames, and so on.

One most common application of rubber seals is creating airtight spaces like the cap of a jar or your car door. If aircraft were not using rubber seals (strips) on their doorways, they wouldn't be able to reach higher altitudes without the cabin collapsing on itself and causing casualties.