9FT Folding Wheelchair Ramp Holds Up to 800 lbs, Threshold Ramp with Support Legs. The middle part of the ramp has four support legs, which gives you a more stable access than a traditional wheelchair ramp. The support legs have 8 adjustment holes with a 1" hole spacing, allowing you to adjust the height according to the stairs. 2.Double anti-slip design, threshold ramp plate is anti-slip design, ramp surface is cover black slip resistance surface, ensure your safty. 3.The bottom transition plate is designed to pass more smoothly and not get stuck....