Special for big ABS prints to prevent them from warping on the edges.
Will hold your big rectangles or quaders on the heatbed.
Put 4 of them separately (not plus!) on your Slic3r or other slicing software next to your .stl you want to print.
Rotate 3 of the Anti-Warping-Edges and move them all by mouse
until they fit on the heatbed to the print objects outer corners.
Zoom may help to place it exactly.
Slice it together with your *.stl to your printer G-code.
After printing use a small saw or rotating tool to get it away from print object.
Hope this will support you a little bit - feedback would be appreciated