A truss has a pair of parallel and longitudinally extending chord rods and transverse rods interconnecting the chord rods. First and second slides each have a pair of tubes each fitting over a respective one of the chord rods and slidable longitudinally therealong and a cross member rigidly interconnecting the tubes and formed with a throughgoing hole through which passes a respective anchor member projecting from a tunnel or mine wall. The slides can be longitudinally fixed on the rods.