Joinery saws
The backed saw family — dovetail, carcase and tenon saws — thin plates held straight by a folded or slotted brass or steel spine, built for cutting precise joints at the bench.
Dovetail saws
A dovetail saw is a small back saw, 8–10 inches in length, filed rip at fine pitch (14–16 ppi) with light set. It cuts dovetail joints superbly and does little else. Even in shops where machines do the ripping and crosscutting, most furniture makers still cut dovetails by hand. It's a mark of true craftsmanship.
Carcase & tenon saws
Carcass and tenon saws complement each other. Somewhat larger and with coarser pitch than dovetail saws, they are often used to cut tenon shoulders in the case of carcase saws, and tenon faces in the case of tenon saws. The typical carcase saw is 10–12 in, filed crosscut, and has a pitch of 12-15 ppi. Tenon saws are larger and more aggressive: 12-16 inches, filed rip, with a pitch of 10-14 ppi. The novice is drawn to finer pitch saws hoping for a precise cut, but in reality, the sawyer's skill has a greater effect and a wise sawyer chooses a lower pitch and gains efficiency.
Unbacked handsaws
The unbacked hand saws, or simply "handsaws" are larger than joinery saws, often 20 - 26 inches from toe to heal and with no spine to halt the cut depth and a long blade, these saws make quick work of cutting stock and glue ups to dimmension. Pitches as low as 4 or 5 ppi are common for hand saws filed for the challenging task of rip cuts, and get a difficult job done with little fuss.
The best handsaws these saws are taper-ground: the plate is thickest at the tooth line and thins toward the back and toe (heal?). Since the body of the plate is already narrower than the kerf the teeth cut, it clears the walls of the cut easily — so a taper-ground saw needs noticeably less set than a flat plate, and rewards you with a thinner kerf, less effort, and a straighter-tracking cut.
What keeps unbacked hand saws straight?
The best unbacked hand saws undergo a process called "tensioning" where internal stress is introduced to hold the saw plate stiff. Light strikes with a curved-face hammer along the spine and behind the teeth on each side of the plate dish the metal, creating secondary structure that resists bending. Similarly, this technique can be used to restore a bent saw plate. The blows must be light and precise to avoid marring the plate.