Abstract: A pillar intended to form part of a furniture support, particularly of a seat, and composed of a sliding tube whose frustoconical top end is intended to be engaged with a force fit, by its top part, in a matching frustoconical cavity in the top part of the piece of furniture, and which slides in a support tube fastened to a foot of the piece of furniture. The sliding tube holds captive, with radial clearance, the body of a gas spring whose piston rod is fixed to the bottom of the support tube. A metal reinforcement sleeve is engaged with a force fit inside the frustoconical end part. Its bottom edge serves as a support surface for the top edge of the gas spring body. It is advantageously composed of a split bush carrying a tongue which secures against rotation a pushrod interposed between the locking control finger and an actuating lever.