Your old hacksaw dull blades can still be very useful and come in handy when you building a workshop helper.
Like in this case in my workshop notes caddy (look it up in my Projects), I used a piece of an old hacksaw blade for cutting paper. Another use for them will be for cutting sandpaper etc.
So don’t throw them away, keep them in a draw and one day you will need them.
-- Stelios L.A. Stavrinides: - I am not so rich to buy cheap tools, but... necessity is the mother of inventions