The Spacer is normally made by foam materials. The purpose of spacer is to create a pre-determined gap in between two substrates. In certain designs, gap is necessary for some purposes, ie to allow some objects to be inserted in between the two substrates afterward.
Suitable foam material and thickness of foam shall be selected correctly to ensure the ideal gap is created.
Normally, the spacer is designed with at least one surface with adhesive for its to be stuck to one of the substrates.
For the spacer with adhesive, it could be supplied either in full cut pattern or half cut pattern (few pcs in a sheet).