Kwik Goal Flat Rectangle Markers (10) The 16A30 Flat Rectangle Markers are designed for all types of training. They can be used to set up boundaries for a field or grid. The ball rolls smoothly over the 16A30 Flat Rectangle Markers. The gripped back of the 16A30 Flat Markers help prevent slippage on some surfaces.  The 16A30 Flat Rectangle Markers come in sets of 10 per color — available in red, white, blue, and yellow.