Clear Burglar Bars have heat-resistant and flame-retardant properties. A potential intruder would need to continually hold the flame on the individual bar for many minutes in order for a sufficient weakening to occur. If an uninstalled bar is then severely twisted, it will break at this weakened point. An installed bar, however, will be required to be beaten or kicked at this burned point, a noisy procedure requiring a great deal of effort. Polycarbonate will immediately cool & harden, turning black & hard once the flame is removed – thus a hole cannot be made in the bar, but the bar will be rendered more fragile than usual at the place it was burned.