a roof as shown in fig3 a 3 b and 11 the actuation members 4 comprise a first lift structure 30 mounted on a base 13 fixed relative to the structure 2 a second lift structure 19 is operatively connected to the first lift structure 30 and is actuable to be raised and lowered relative thereto for raising and lowering the cover 3 supported thereon a third upper lift structure 15 is operatively connected to the second lift structure 19 and actuable to be raised and lowered relative thereto a rotatable guide such as a pulley 23 is supported adjacent a top end of the second lift structure 19 and a first flexible tension member such as a cable 16 is connected between the first structure 30 or the base 13 and extending about the rotatable guide 23 for connection to a lower end 21 of the third lift structure 15 drive means 40 powered by a motor 31 is provided for driving the second lift structure 19 to be lifted and lowered relative to the first lift structure 30 and in doing so lifts the rotatable guide 23 to passively cause the cable 16 to lift the upper lift structure 15 relative to the second lift structure 19 as shown in fig3 a 6 and in one embodiment the actuation members 4 comprise a rack and pinion.