Steel for Strength! Trussing in both Compression & Tension  prevents sag!

Gates are hung in cantilever. This means that the gate is supported at only one end.  Because of this, especially for wider gates, the hinges must be strong, the frame must be strong and solid cross bracing within the frame is a must. 

Most gate frames utilize a cable that spans from the top hinge corner to the bottom corner of the unsupported end of the gate.  This approach attempts to control sag  through tension by holding up the bottom corner of the unsupported end of the gate.  This approach only addresses the force of tension that is being placed on the gate, but ignores the considerable compression force that is in play when a gate is installed.  An approach, that only addresses tension, will work for a while until the cable stretches and/or the corners give way.  The only way that this approach will work over time, is to install a support foot or wheel for the gate at the unsupported end.

A gate built with a true truss frame utilizes strong hinges, a strong frame with solid corner connections, and solid cross bracing (that cannot stretch) that extends from corner to corner each way. This addresses the forces of both tension and compression that is placed on the gate once it is installed.  With this approach, a support foot or wheel will not be required.

Most of the popular steel gate frames offered for sale in the market are not utilizing true truss technology which is required to effectively address gate sag.  .