apparatus for releasably clamping a range of sizes of complex shaped articles having an upright web and laterally disposed upper and lower flanges . a first set of upper and lower flanges of an article placed on a work platform extends towards a first edge of the platform and a second set of upper and lower flanges extends towards a second edge thereof . one c - clamp on one side of the article terminating at a tip end is movable between an inactive position distant from the work platform and an active position at which the tip end grippingly engages one of the lower flanges of the article . as the c - clamp moves between the inactive and active positions , the tip end follows a path other than a continuous smooth arc so as to avoid striking the upper flange of the article . another c - clamp , similarly constructed and operated , is provided on the other side of the article . an actuator is selectively operable to move each c - clamp which has a pair of cam followers slidably engageable with a shaped cam slot on a support plate integral with the work platform . a plurality of such clamps can be used at a plurality of spaced locations to fix an elongated article to an elongated work platform .