A method and apparatus is disclosed for controlling the angle of a pivoted, pendant supported extensible boom and the mast-boom angle between working positions and a transport position. The structure for controlling the angle includes a wire rope driven by a winch and trained over a boom supporting hoist and over a pendant take-up hoist which includes a floating sheave assembly connected to an extensible portion of the boom by a fixed length pendant. Another fixed length pendant determines the mast-boom angle when the boom is in working position, and a floating sheave stop is pivoted to the mast in position to cradle and/or abut a portion of the floating sheave assembly for enabling complete control of the mast when moved between its transport position and working positions relative to the boom.