Frame : There are two types of Hacksaw Frame, a fixed and an adjustable. The fixed frame can only take one length of Blade, but is more rigid that the adjustable type, which can take Blades of different lengths.
Blade : There are also two main types of Blades, but in the case of both, the teeth on the Blade are facing away from the Handle towards the front of the hacksaw.
The first type of Blade is the All Hard Blade which has been hardened throughout. As a result there is more efficient cutting but the blade tends to break more easily.
Plumbing and pipes do not always come apart easily so investing in a good quality Hacksaw will be extremely useful when cutting any type of pipe, nut, bolt, or screw. In a tight squeeze you can always remove the hacksaw blade and use it on its own.