16-inch ground system components. Connections are steel spigots & 3/4-inch clevis pins. In order to properly use ground support systems, the truss must be level during lift and at trim (unless it has been specifically designed for other orientations). Below are some guidelines to be followed in order to properly use ground support systems. The first step when erecting a ground support system is to select a site which has a minimal difference in grade. Sites with large slopes or mounds and depressions should be avoided or leveled prior to erecting the system. Once a level site is selected, the locations of the bases should be determined.