floating shelf       
noun [ C ] uk/ˌfləʊ.tɪŋ ˈʃelf/ us/ˌfloʊ.t̬ɪŋ ˈʃelf/
 (用隐藏起来的钉子或螺丝固定在墙上,而不是用支架支撑的)置物架,浮架
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。 
 - More examples
 - Light-coloured floating shelves create interest in this dining area.
 - The bed frame is made from American black walnut and the headboard incorporates floating shelves on either side.
 - She suggested a few built-in floating shelves and lilac paint.
 - What sort of storage do you want? Basic bracketed shelves? Shelves in a chimney breast recess? Floating shelves?
 - Floating shelves won't take heavy weights.