Abstract: An extensible and retractable strut comprising telescoping pairs of members the outer of which carries a manually operable collar that is slideable between locking and unlocking positions. The collar carries a manually-releasable pivoted locking lever having an offset end that can be received in an opening of the outer member to lock the strut in adjusted position against release when the collar is in its locking position. When the collar is in the unlocking position, the offset portion of the lever is out of registration with the opening and instead bears against the exterior of the outer member. For such circumstance the members are relatively moveable between their extended and retracted positions. A keying means carried by the collar is engageable with cooperable means on the outer member to maintain the collar in a given aligning position.