Security restraints were straps that secured sickbay patients to their beds.

In 2267, James T. Kirk ordered Doctor Leonard McCoy to use security restraints on a pain-ridden Spock after the erratic Vulcan escaped sickbay. Later, more in control of his faculties, he apologized and told them that neither the restraints or sedatives would be necessary. (TOS: "Operation -- Annihilate!")