ankle rack (noun) device used to lock a girl's ankles in wooden stockage. Girls who have been repeated runaways may be held in place to have their tendons cut or feet amputated.

"Bring an ankle rack," said Ulafi to one of the guardsmen. One was brought. 
"Put her in it," said Ulafi. 
The guardsman removed his neck strap from her throat, freeing, too, her ankles. He untied her hands. Lifting her under the stomach he held her ankles near the rack; another guardsman placed her ankles in the semicircular openings in the bottom block and then swung shut the top block, with its matching semicircular openings, over them. He secured the top block, hinged at the left, to the bottom block, with a metal bolt on a chain, thrust through the staple on the lower block, over the hasp, swung down from the upper block. 
Book 13, Explorers: pg 46