A line of bricks placed horizontally as part of a wall is a 'stretcher' - this is the 'future' for the individual bricks carried in a HOD (the 'bearer') and '(O)ught' is 'in' the HOD = HO(O)D def. 'cover'
... having checked Chambers, perhaps the 'stretcher' is a single brick but it only operates as such within a wall structure, so I think the principle works ok.