Kirk and the landing party with guns in holsters
A holster was a type of belt with a pocket on one or both sides used to carry hand-held firearms.
Starfleet landing parties also wore holsters to hold phase-pistols, hand scanners, and communicators. (ENT: "Terra Nova")
Uniforms of the Andorian Imperial Guard were equipped with holsters for their sidearms. (ENT: "The Andorian Incident")
Garos and his Malurian henchman wore holsters during the firefight with Jonathan Archer on the Akaali homeworld in 2151. (ENT: "Civilization")
The 22nd century Nausicaans were also wearing holsters for their directed energy weapons. (ENT: "Fortunate Son")
In 2268, James T. Kirk, Leonard McCoy, Spock, Montgomery Scott, and Pavel Chekov were given holsters as part of the Melkot re-enactment of the Battle at the OK Corral. (TOS: "Spectre of the Gun")