You can see the legs are recyled timber from other parts of the project screwed together so that it can be re used again. Centre lines are marked and a stringline will be run along the strongback so that the legs can easily be centred. Once all the legs are attached to bulkheads (and temporary bulkheads) it is just a matter of standing them in the correct position, making sure they are square, level and plumb by the stringlines and screwing them to the strongback.