Roughly 15 years ago, I was walking across either …

Roughly 15 years ago, I was walking across either S-10A or C. At the time, it had these unusual tiedown eyes and a huge set of rollers on the top of the structure, along with yellow paint outlining several areas. There was also a sign that said something along the lines of "make sure truck is secure before operating gate". After scratching my head for a few minutes, I concluded that the gate was operated by putting a pickup truck's drive wheels on a set of rollers, securing the truck against movement, and then using the truck to open and close the gate.