The pad should compress the _canal_ and be convex if the patient is stout. Its size ought to be sufficient to compress the canal and the margins for a short distance on each side, but the pad should be as small as will ensure fair compression. A very flaccid bellywall, and a large gap or protrusion require a large surface on the pad. The _spring_ should be supple and padded behind to rest on the two sacro-iliac synchondroses, without bearing on the spine. The spring, narrowing as it comes forward, embraces the pelvis; and opposite the anterior iliac spine inclines downwards, because the hernia is a little lower than the resting-place of the spring behind. When the rupture is almost reached, the spring takes a slight elbow or bend (the neck), that its pressure may be directed against the hernia more fully. _Understraps_, generally not necessary, should be omitted if possible. In trusses for children when the testis is not descended, the pad should have a notch at its lower border in which the testis may rest uncompressed. In the truss for _femoral hernia_, the _spring_ bears behind the body and encircles the hips in the same manner as in the inguinal truss, but when opposite the femoral artery it turns abruptly downwards to reach the saphenous opening. The _pad_ should fit the hollow where the rupture issues and be not oval, but rounded. The _under-strap_ should be attached to the stud at the lower end of the pad, and pass round the perinæum and fold of the buttock, and be attached to the neck of the spring close to the pad. It should be made of knitted bandage that it may be changed and washed frequently. _When measuring_ a patient for an inguinal truss, the circumference of the body round the hips (between the crista ilii and the great trochanter) should be first taken, and then that between the symphysis pubis and the anterior iliac spine, half of which distance denotes the position of the internal abdominal ring, which with the inguinal canal has to be supported by the pad of the truss. For a femoral hernia the same measurement should be taken round the body, and also the distance of the saphenous opening from the symphysis pubis and from the anterior superior iliac spine. This will enable the maker to put the pad at the proper angle with the spring, so that it compresses the saphenous opening, and clears the crest of the pubes. Every patient should, while he wears a truss, show himself from time to time to the surgeon to see that any defect in his apparatus may be quickly remedied. It is a useful precaution also to keep two trusses at hand, so that if one breaks, the patient may at once apply the other.