Our threshold ramps provide an easy and safe transition for interior or exterior door thresholds, plus small steps inside and outside the home. National Ramp offers two aluminum threshold series for consumers. The series includes 12 different options to meet your sizing needs. With eight fixed height models from ½ inch to 2 inches and four all-thread adjustable leg models from 1 ½ inches through 6 inches, we have a ramp for every bump. These aluminum step ramps are perfect for small rises and are suitable for up to two steps or about 15 inches in height.