A handgun holster is a device used to hold or restrict the undesired movement of a handgun, most commonly in a location where it can be easily withdrawn for immediate use. Holsters are often attached to a belt or waistband, but they may be attached to other locations of the body (e.g., the ankle holster). Holsters vary in the degree to which they secure or protect the firearm. Some holsters for law enforcement officers have a strap over the top of the holster to make the handgun less likely to fall out of the holster or harder for another person to grab the gun. Some holsters have a flap over the top to protect the gun from the elements.