Derived from the design of the repair facility used during the First Tiberium War, the service depot serves the same purpose of repairing GDI vehicles. In the Second Tiberium War, the newly designed Orca Carryall was utilized to carry vehicles from conflict areas to service depots for repair.
The service depot is a circular platform where vehicles are repaired. Repairing a unit takes far less resources than building a new unit, but still requires some resources. If a GDI commander runs out of credits while repairs are being performed, repairs will cease until more credits are acquired. The building itself is not heavily armoured, and require a larger area around it to maneuver vehicles in the line, being an open design.
It is possible to sell vehicles at the service depot. Once a vehicle gets to the repair pad, the player can sell it by placing the sell cursor over the vehicle until the cursor turns green and slightly smaller. This function was accidentally transferred to the Allied service depot in Red Alert 2, which was based on the Tiberian Sun service depot code-wise. This was not disabled until the Yuri's Revengepatch 1.001.
Nod service depot concept art
GDI service depot concept art by Jack Martin
In snow theatre
Despite being only available to GDI, there is a Nod version of the icon that is used when a Nod player captures a GDI construction yard. This is the only object in Tiberian Sun that has a different icon for a faction that can not normally build it.