The method here described has some advantages over the present standard method of designing with continuous spars. Firstly, it gives lighter spars by working as many points as possible up to the elastic limit. Secondly, it is far quicker to use owing to the necessary formulæ and processes of computation being more manageable and to the fact that practically each bay can be designed separately without affecting the others. Thirdly, the roughing out and the final checking are done with the same set of formulæ, whereas, if the usual type of spar construction is adopted, it is necessary to use different methods for the preliminary and final design. Fourthly, the accuracy of the work is not affected by the supports getting out of line when the whole structure deflects under load, a serious error in the older method being thus avoided.