T-rail refers to an aluminum extrusion that is in the shape of an inverted T. They are designed for Styrofoam plug trays that are stiff enough to span between the extrusions.
A base of steel bench legs and runners is required to support the trays. T-rail benches are fixed. The trays can be slid from the center aisle of a greenhouse to the sidewall or to one end for pickup and transfer.
This system is used for intensive large scale transplant production.