A stall is a stand that NPCs use to display their product. The majority of stalls can be stolen from with appropriate level in Thieving. Items sold include: silk, fur, scimitars, fish, vegetables, etc. Most types of stalls can be found in Ardougne however there is also a selection in Rellekka, Miscellania, Sophanem, Draynor and Taverley. Stealing from a stall may alert a nearby guard who will attack until they die, you unsuccessfully pickpocket them, or the area is left. To prevent guards/merchants from noticing you, thieve with the stall between your character and the NPC. Stall owners will not talk to players if they have stolen from their stall within the last 20 minutes unless you have a vial of stench (a). It's not needed for the stalls found on Ape Atoll.
Note: In Keldagrim, stalls often differ in respawn time and their experience given. The silver stalls respawn twice as fast, but yields half the experience. The bakery stall, however, respawns half as fast, and gives the same experience.