noun
fulcrum peg; oarlock pin
A wooden peg fitted into a cavity in an oar, used as part of a traditional Japanese oarlock (入れ子). This is a specialized nautical term.
See also: 入れ子
和船では、櫓杭を入れ子に差し込んで櫓を漕ぐ。
On a traditional Japanese boat, you insert the fulcrum peg into the oarlock and row.
入れ子 is the oarlock itself, while 櫓杭 is the peg that fits into it.
Compound of 櫓 (ro, 'scull') and 杭 (kui, 'stake, peg'). The reading ろぐい is a standard rendaku form.