Restringing is a method of doll repair that consists of replacing loose elastic cord inside a doll with new or tighter cord. This is also used to reattach a doll's broken-off limb.
Reasons for Restringing
The dolls are semi-strung with elastic cords in the arms and legs, allowing a wide range of movement that cannot be done with flange joints. Vigorous play or constant reposing and moving of limbs can lead to the elastic in a limb becoming loose over time. Loose elastic means that arms will not hold position and legs, once extremely loose, will not be able to hold the doll up to stand on her own.
If the elastic cord frays or breaks, limbs will fall off. Restringing is used to reattach the broken limb.
As of 2009, American Girl no longer uses metal clamps in the joints; the elastic is simply knotted. This means that limbs may become looser quicker. People may restring in order to add their own metal clamps or tighten limbs.
A customized doll cannot be repaired through the hospital, and so must be done by outside repairs.
Through American Girl
The American Girl Hospital will do restringing under "Limb Reattachment" and "Wellness Visit". This costs a flat fee regardless of the amount of limbs needing restringing. However, when dolls return, they will no longer have a plastic cup. Instead, they will have two plastic pieces on each limb holding the string.
Through Other Means
Other collectors sometimes offer restringing services for a lower cost than the Hospital, often offering discounts for single limbs. Also, a collector can do it themselves.
How to Restring
Tools needed are brass clamp ferrules and washers (two per limb), a heat source such as a blow dryer, wire clamps, a clamp, and 1/8" elastic cord. The cord is available through many doll repair outlets both online and offline; the other items are easily purchased at a hardware store.
The doll's head must be removed and the internal stuffing taken out and kept. This gives access to the strings of the doll through the neck. Each limb needing restringing will need the elastic inside cut and then removed. The limb will detach from the cloth body and vinyl cup, leaving a loose cup in the limb and a loose cup internally. The loose cup must be removed from the limb; the vinyl is generally heated to allow a smooth removal. The elastic is then replaced, clamped into place with the ferrule, and the limb cup is replaced into the limb. The elastic is guided through the hole in the joint cup and the internal cup, pulled tight, held in place with a clamp, and the ferrule is clamped down. Once all desired limbs are restrung, the doll is restuffed and the head replaced.
A complete guide is available here.