Mast
noun
The pillar the sail is attached to is called a mast. Without it the sail wouldn't do it's job and your sailboat wouldn't move at all.
ほばしら
The readings for this word are both kun'yomi readings. You learned these readings with other vocabulary, so you should be able to read this on your own.
この木は帆柱にちょうどいいぞ。
This tree is perfect for a mast.