1. On top of indicates a position higher than the object.
Pattern: verb + on top of + noun
They put the blanket on top of the sheets, and the bedspread on top of the blanket.
I’m sure I left my keys on top of the desk.
to be on top of something—to be sure about one's knowledge or control of something Her son had a hard time learning math, but he is on top of it now.
Surprisingly Scary Short Stories
Surprisingly Scary Short Stories 14
The doctors told the amputee he might experience a phantom limb from time to time. Nobody prepared him for the moments though, when he felt cold fingers brush across his phantom hand.