squeeze box

At caving conventions aboveground, cavers often squirrel themselves through adjustable wooden "squeeze boxes" in good-natured competitions. In the safety of this controlled setting, cavers may push their capacities far beyond what they might hazard underground; […] A very slender woman's tightest squeeze may be defined by the width of her skull turned sideways. Some women thus emerge from squeeze boxes, triumphant, with mirrored abrasions over their cheekbones.

Jebby rushed to the area behind the mare's paddock. What he saw there filled him with fresh concern. Isabella was in the "squeeze box." This, he knew, was a strait jacket for animals! […] He had seen the old squeeze box sitting in the field behind the hoofed animals' paddock. Zoo keepers had used it in the days before the invention of the Tranquilizer Gun for immobilizing animals when they wanted to inoculate them or treat them for illness or injury. If the squeeze box were used unwisely, a Zoo keeper had told Jebby, an animal inside it could be squeezed almost to death. And it always caused panic as the wooden sides pressed against the trapped creature's body.