The boom attaches to the mast with a fitting called a gooseneck. The gooseneck allows the boom to swing far out to both sides as well as to pivot up and down.
This photo also shows the vertical slot in the mast used to hold the mainsail's front edge (the "luff") to the mast (as you’ll see in Part 2 of this course). The sail “slugs,” fittings on the sail's luff, slide up the mast in this slot.
A similar slot can be seen in the top of the boom, to hold the foot of the sail.
The L-shaped metal pin at the forward end of the boom holds the forward bottom corner of the mainsail, called the tack.
Note the two lines (never called “rope” on a boat!) running up the mast. These are the halyards, described in the next page.