When a character's thumb is inserted into their legwear's beltline (i.e. at the top of their hip), either to remove that piece of garment or as a some sort of "dynamic" posture (such as [[hand on own hip]]).

Note that this tag only applies if the thumb is on the beltline position, and as such it is not applicable when character is moving their thumb below that area (such as [[panty pull]]).
thumb in beltline