Abstract: A T-shaped fixing is formed of a first strip of plated steel providing a T-head limb and a second strip providing a T-stem limb. The limbs are connected by folding the steel double at one edge of the T-head strip and them folding the steel at right angles at the line joining the two limbs. To one side of the stem limb, the line is provided with a series of punched apertures to which pins are fitted. To the other side of the line, the head limb is provided with apertures for screw or rivet fixing of the fixing. The stem limb can also be provided with apertures. For use in insulating a square section duct, its corners are provided with fixings, with flanges having the pin apertures extending downwards at the lower corners and outwards at the upper corners.