Abstract: A covering sheet for applying to a selected surface in substantially fitted, covering relation consists of a flexible sheet of predetermined size and thickness, having a rectangular grid of lines to provide rectilinear yield lines (lines of weakness) extending in a first direction and in a second direction at right angles to the first direction, to enable tearing by hand along selected ones to the grid lines as a tear in a first direction, the sheet having individual perforations extending completely through its thickness, and located at the points of intersection of the axes of the lines of weakness. The perforations facilitate changes in the direction of a tear at a selected point of intersection, to extend the tear in the second direction, to achieve a desired size of sheet.