The Truth Hardware (AmesburyTruth) 15 Series Entrygard Left-Hand Dyad Casement Window Operator (15.11) is specifically designed for use in casement windows, working seamlessly with AmesburyTruth 14 Series Casement Window Hinges. Commonly referred to as a split-arm window crank, mechanism, or opener, this left-handed dyad operator is engineered to support window sashes up to 45 lbs (20.4 kg), with widths ranging from 9" to 24" (228.6 - 609.6 mm) and heights up to 67" (1701.8 mm).

This operator is commonly identified with the stamp "31782L" on the arm, though it may also feature alternative markings such as 20544, 20810, 30636, 30637, 30830, 30841L, 30843L, 31368, 45275, TH-23078, TH-23079, or PAT.NO. 4.840.075.