Kwik Goal Flat Corner Markers (4) The 16A31 Flat Corner Markers are designed for all types of soccer training. The 16A31 Flat Corner Markers can be used for setting up a small field or a grid. The balls roll smoothly over the 16A31 Flat Corner Markers. The gripped back of the 16A31 Flat Corner Markers help prevent slippage on some surfaces. The 16A31 Flat Corner Markers come in sets of 4 per color. The 16A31 Flat Corner Markers are available in red, white, blue, and yellow.