This meniscus is baby-sized, and totally unnoticeable by toddlerhood. To put on a Gomco, the foreskin is grasped with medical tweezers and then a slit is cut in it. After that the bottom half of the clamp is fitted under the bottom of the foreskin, then the heavy top is screwed on until the clamp cuts off the circulation and makes a perfectly circular template around which the foreskin could be cut even by the unskilled. You could even do it without causing any harm, because you cannot cut through a quarter inch of surgical steel to accidentally cut the penis. I have seen doctors apply the clamp and then the father cut the foreskin.
Doctors often use anaesthetic as well.
This is theoretically to reduce the trauma of the circumcision. However, realize that everything you add to the procedure adds discomfort. Here is how anaesthetic usually works. A precious few Jewish doctors use the Magen clamp. Sometimes a mohel will use the Magen shield as well, depending on whether the anatomy of the penis is such that the shield or the clamp is indicated.