An arched girder, such as that in Fig. 48, is technically termed a "bowstring girder." The curved part is a cast-iron beam of T form in section, and the horizontal line is a wrought-iron tie-rod attached to the ends of the arch. This girder has but little to commend it, and is by no means worthy the confidence placed in it by builders, with many of whom it is quite popular. The brick arch usually turned over it is adequate to sustain the entire compressive force induced from the load (the brick wall built above it), and it thereby supersedes the necessity for the iron arch, which is a useless expense. The tie-rod is the only useful part of the bowstring girder, but it is usually made too small, and not infrequently is seriously injured by the needless strain to which it is subjected when it is "shrunk in" to the sockets in the ends of the arch. The bowstring girder, therefore, should never be used.