Zutter Round-it-All / R10 Corner Rounder Tool
Made to specifically round corners on heavy-duty materials, the Round-it-All will make rounded corners in chipboard, Zutter's acrylic, Canvas Artboard, Clipboard Wood, and multiple sheets of cardstock. Use your little rounder on single sheets and photos - this one is for the big jobs. R10 (Pink) makes a-1/2-inch corner, while the R5 (Blue) makes a-1/3-inch corner.