23 of the tubular channels 20 can be directly placed if desired for the purposes of supporting the suspended shutter units 10 however in the example of the structure illustrated by the drawings there is disposed through a bore in each rim 23 of the tubular channels 20 a screw 30 for the purpose of applying tension between the rims 23 and the horizontal member 28 28 39 of each t shaped rail 24 24 39 the screws 30 can be set at tension sufficient to allow the sliding of the shutter units 10 10 39 along the horizontal members 28 28 39 without allowing the shutter units 10 10 39 to be so loosely affixed as to wobble it will be appreciated that the screws 30 can be replaced with a bolt pin clip or other appropriate means the screws 30 could be modified if desired by providing a pad at their bottoms to facilitate the sliding of the shutter units 10 10 39 along the t shaped rails 24 24 39 by reducing the friction created between the bottom of the screws 30 30 39 and the horizontal members 28 28 39 in the illustrated structure the t shaped rails 24 24 39 of the overhead shutter suspension assembly 12 are affixed vertically to the underside of a suspension rail or beam 32 as best shown at fig8 the suspension beam 32 is substantially flat and rectangular in section the suspension beam 32 of the overhead suspension assemby 12 is formed integrally and radially with a cylindrical portion 34 in the example of the structure shown the cylindrical portion 34 of the horizontal beam 32 is fitted within a cylindrical socket 36 suitable for pivoting the suspension beam 32 within the socket.