Hollowback the normal cased book is a hollowback but this is assumed and therefore not specified. See back.
一般精装书籍均假定为空背，不用特别说明。参阅书背。
2
I sneaked out a quart jar of peaches, some cold corn bread, and a few Onions, and started up the hollowback of our house.
我偷了一罐桃子、几块冷玉米面包和一些洋葱，打算从后门走。
3
Back then they were made of naturally occurring objects - coconuts, sea shells, hollow stones or similar objects filled with moss or a similar material that was soaked with animal fat and ignited.