Spile, sometimes called a cask peg, is a wooden or plastic peg intended to manually control the venting in and out of carbon dioxide (CO₂) and air from the shive hole during the conditioning and dispense of traditional cask beer. See shive. Spiles have a tapered conical shape approximately 20–30 mm long to fit in the shive hole and are manipulated by hand and mallet.

There are two types of spile. “Soft pegs” are made from a very porous wood such as cane, bamboo, or sapwood, which allows casks to vent off CO₂ slowly during the conditioning period. “Hard pegs,” made from hard wood (oak, sycamore) or nylon, retain condition (CO₂ gas) in the beer and exclude air when the beer is not being drawn out. Wooden spiles are discarded after a single use, but plastic spiles can be reused after appropriate cleaning.