Membrane blanket

Provided by the ASK Keyboard Dictionary

Aka/also known as: rubber mat, rubber sheet

The membrane blanket (or simply blanket) is a possible sheet of usually rubbery material inside a keyboard assembly that dampens the stress key-switches' actuators (such as the pivot plates on buckling spring keyboards) can exert on the membrane assembly. They can be black, grey or white coloured. At least for Model M keyboards, they can operate without a blanket but a Unicomp employee has stated they cannot reach their rated key-press lifetime without one. Its presence or lack of and its exact material can affect key feel.

Sources

ASK. Admiral Shark's Keyboards original content. License/note: CC BY-NC-SA 4.0.