a shelf that is fixed onto a wall using nails or screws that cannot be seen, rather than being supported by brackets (= L-shaped pieces of metal, wood, or plastic)

A board from a dresser that won't fit in your apartment can be transformed into a floating shelf. 餐具柜上的木板，如果在你的公寓里放不下的话，可以改造成钉在墙上的浮式置物架。