The invention concerns a punch device that includes an actuating member of flat proportions, a penetrating tool with a sharp tip carried by the actuating member, a compressible spacer attached to the surface of the actuating member alongside the penetrating tool and mounting means for mounting the punch device on a glass sheet with the tip of the penetrating tool directed towards the glass sheet. The arrangement is such that a force of sufficient magnitude applied to the actuating member in an axial direction towards the glass sheet compresses the spacer and drives the tip of the penetrating tool into contact with the glass sheet thereby to break the glass sheet. In one application the punch device can be used to break an emergency exit window in a bus.