Abstract: Modifications in a levelling device for ladders and the like are provided. Apertured lug, adapted for attachment to the bottom ends of uprights, stiles or legs of a ladder, trestle, etc., are slidably mounted on an arcuate support bar, and biased to a non-locking or freely slidable position. On application of weight to the ladder, the apertured lugs pivot to a locking position. In one embodiment, each of the apertured lugs is formed with extension members or fingers with abutment surfaces extending parallel to the plane of the ladder which tangentially engage the sides of the support bar when the apertured lugs are in locked position to prevent or limit any tiltable movement of the support bar out of the plane of the ladder. In another aspect of the invention, the lugs are provided with non-circular apertures and the support bar is formed with a complementary non-circular cross-sectional configuration, such as triangular, square, etc.

Abstract: A levelling device for ladders has a pair of locking bars (24, 32, 51, 52) pivotally mounted on the ladder (28, 31, 42). A support arc (16, 33, 48), having feet (19, 34) at each end, passes through apertures (50) in the locking bars (24, 33, 51, 52). Springs (25, 46) interconnecting each locking bar (24, 32, 51, 52) and the ladder (28, 31, 42) urge the locking bars (24, 32, 51, 52) to an unlocked position where the support arc (16, 33, 48) is free to pass through the apertures (50). When weight is applied to the ladder (28, 31, 42), the locking bars (24, 32, 51, 52) are urged to a locked position, against the springs (25, 46), where the sides of the apertures (50) engage the support arc (16, 33, 48) to lock it against further movement. By adjustment of the support arc (16, 33, 48), the feet (19, 34) may be raised or lowered to accommodate any irregularities in the support surface so that the ladder (28, 31, 42) will stand vertically.