in the 1760s a period of expansion began, leading to a configuration which (despite subsequent rebuildings) can still be seen today : five slipways, four dry docks and a wet basin (slipways were used for shipbuilding, but the main business of the eighteenth-century yard was the repair, maintenance and equipping of the fleet, for which the dry docks and basin were used). one slipway (1774) survives unaltered from this period (slip no.1): a rare survival. it is covered with a timber superstructure of 1814, a similarly rare and early survival of its type; indeed, only three such timber slip covers have survived in britain, two of them at devonport (the second of these, of similar vintage, stands over the former no.5 slip; it was later converted to house the scrieve board, for full-size drafting of ship designs). the two additional docks were added, north of the double-dock, in 1762 and 1789 (both subsequently rebuilt).