KanjiJLPT N1
Board

board, load (a vehicle), ride

Mnemonic

Your hand parts the tall grass blocking the dock entrance. Everything seems to fit into place—the gangplank aligns perfectly—and you board the ancient riverboat, climbing aboard with a confident step.
Additional thoughts
Picture yourself physically pushing grass aside with your hand, then feeling the satisfying click of the gangplank fitting into place before you step on. The sequence hand→grass→fit→board mirrors the order of climbing aboard.
Quick recall
A hand parts the grass, the gangplank seems to fit, and you board the boat.

Details

The keyword for 搭 is board. This kanji refers to the act of boarding or getting on a vehicle, vessel, or aircraft. It conveys the idea of mounting or riding, as in stepping onto a mode of transportation. It is commonly associated with the concept of embarking on a journey by climbing aboard something.
On'yomi
とう