extension leg; add-on leg
A detachable or foldable leg used to extend the height or reach of an apparatus, such as a tripod, ladder, or furniture.
I extended the tripod's extension legs and adjusted the camera height.
tsugi-ashi; sliding step
In martial arts such as kendo and judo, a footwork technique where the back foot is drawn closer to the front foot, followed by a large forward step, used to close distance smoothly.
In kendo, you use tsugi-ashi to quickly close the distance.
Compound of 継ぎ (tsugi, 'joining, splicing') and 足 (ashi, 'leg, foot'). The martial arts sense is a specialized application of the stepping motion.