The saw by design is single sided and the blades can be replaced without tools in most cases,
hence the supply of the blades only.
A saw designed by the Japanese, I guess about the 16 century along with is associated family of Coping saws and fret saws.
They are designed for fine woodworking and are not really pit saws by any means.
The are part of te family of saw having replacable blades
The cutting teeth face different directions to a standard pane or Jack saw.
Of which has advantages of prodicung a accurate cut, although a hack saw can be reversed to produce the same effect.
Have used this saw for a number of years. Finally after cutting a large number of laminate 8 mm boards it was time for blade replacement. An easy to use saw with a comfortable grip. Blade changeover simple.