the covering to correct any skew that may be inherent therein the head rail 22 for the covering as possibly best seen in fig8 includes an arcuate front wall 54 connected to a rear component 56 and a top wall 58 the space between the front wall and an open rear of the head rail along the bottom of the head rail is also open so the fabric for the covering can be rolled onto or unrolled from the roller 24 through the open bottom of the head rail end caps 62 are also provided at opposite ends of the head rail for aesthetics the front wall 54 of the head rail 22 again as probably best seen in fig8 has an arcuate main body 64 continuous upwardly with an inclined flat segment 66 that is in turn continuous with a generally flat upper ledge 68 that interconnects with the top wall 58 of the rear component 56 of the head rail in a conventional manner adjacent to the uppermost edge of the inclined flat segment 66 of the front wall a generally inverted t shaped rib 70 extends inwardly perpendicularly to the inclined flat segment and defines a downwardly opening pocket or groove 72 for receipt of the horizontal tab 50 along the upper edge of the skew adjustment device 36 as will be more clear hereafter adjacent to the lower edge of the arcuate main body 64 of the front wall of the head rail is another generally t shaped inward projection 74 which defines an upperwardly opening seat or groove 76 for the lower edge of the skew adjustment device the front wall 54 of the head rail 22 is preferably an extruded member that can be made from aluminum plastic or other suitable.