Patented & High-Quality: Made of premium, high-temperature resistant resin plastic that won’t melt or warp under direct iron heat. Non-Slip Surface: Holds fabric securely while remaining flat enough to press sharp creases for accurate hem widths and turned edges. Heat-Resistant: Withstands temperatures up to 428°F/220°C and tolerates short - term ironing up to 536°F/280°C. The ruler will remain hot for a few seconds after ironing. Precise Details: Corner notch and markings allow easy measurement of ¼"" seam widths. Angles of 30°, 45°, and 60° can be pressed with rounded corners. Easy to Use: Fold fabric over the ruler to the desired hem depth, then press with a dry or steam iron for precise seams, hems, and folds.