Abstract: A development drafter for use in the sheet metal works of ducts, pipings and tubes includes a long tape of flexible strip and a plurality of pins. The flexible strip is in continuity along the direction of the length provided thereon with equispaced and integrally formed a plurality of parallel tubular pin holder portions extending in the direction of the strip breadth. The pins are respectively frictionally inserted in the pin holder portions and have at each one end a head, and have the length longer than the breadth of the strip. By working with the drafter to gauge a working object a development elevation of the object can be quickly and effectively obtained.