Clamps onto beam 5/8" to 1-1/2" thick of any length. General's adjustable trammels accurately measure and mark distances that are too great for conventional compasses and dividers. For layouts, marking templates, and drawing large circles. 6" off-center eccentric points provide fine adjustment. International products have separate terms, are sold from abroad and may differ from local products, including fit, age ratings, and language of product, labeling or instructions.