Engagement has taken place and the leading part of the head is below the level of the ischial spines.

Application of the forceps when the head is not engaged is known as ‘high forceps’. In this situation the pelvic axis necessitates traction ‘round the corner’, so some forceps have detachable handles on rods which allow traction in the correct direction. Although high forceps delivery has been abandoned in favour of caesarean section, ‘axis traction forceps’ are still favoured by some obstetricians.

The blades have very little pelvic curve and are virtually an axis traction forceps. A large episiotomy is needed. The shallowness of the curve allows safe rotation in the vagina. Downward traction encourages rotation of the head.

The claw lock allows the blades to slide on each other and correct or encourage asynclitism of the fetal head as required.

This range of movement allowed by the lock makes it possible to apply lethal compression to the fetal head if the instrument is used improperly.

The spinal cord ends at the level of L1–2, and lumbar and sacral nerves descend almost vertically. Anaesthetic injected at levels L3–4 or 4–5 will produce analgesia of the inner thigh areas without risk of trauma to the cord itself. This is sometimes called a ‘saddle block’.