As all good sign makers know, (sometimes through bitter experience) mixing acrylic with metal can cause problems due to differential movement. Yet amazingly, even in the 21st Century some manufacturers of system signs ignore this reality and create huge problems.
Acrylic by nature is highly Hygroscopic and is susceptible to expansion. Manufacturers who rely on a tight fit between an acrylic lens and an extruded metal paper holder have build in quality issues. Sometimes they work fine other times they jam and sometimes the lens will fall out. A grub screw is just a crude workaround for one of the two issues. Whilst this is a cheap way to make a sign, it doesn’t function.
Even in a small door sign an acrylic panel perfectly cut to tolerance might later grow by 1.5mm due to changes in temperature and humidity when the aluminium barely moves. This reality was recognised in the detailed design of the Folio paper holder, which is part of the patented Jigsaw fixing system. The acrylic is held along the edge by a slotted recess which accepts the edge of the stainless steel holder. As the slot is deeper than the return on the steel and the acrylic is undersized the fit is always effective even as the acrylic grows and shrinks. This design feature is unique to Jigsaw Sign System and reflects engineering in the detail. This is the story of the slot.