A printing screen comprises a screen printing foil and a sub-frame component secured to an edge of the foil, wherein the foil is formed with cut-outs defining deflectable parts of the foil to be deflected out of the plane of the remainder thereof, and the sub-frame component comprises a fixed lip upon which part of the foil can be received, a recess into which the said deflectable parts of the foil can be deflected, and a moveable lip defining a series of spaced projections, the moveable lip being moveable to a position in which the projections bear against the deflectable parts of the foil, deflecting the deflectable parts into the recess to secure the foil to the sub-frame component.