I am guessing it's a reel type..
If the bed knife is still in good shape, you can, with a bit of ingenuity come up with a method of sharpening the reels...
If they only need to be sharpened, you can use valve lapping compound and they will lap in easily...
If they need to have nicks removed and reshaped, you mount a sharpening strip, like
The Scotts Classic Sharpening Kit...
Here is a short you tube video ...
YouTube - How to Sharpen a Push Reel Mower: Scotts Classic
Those can be fun old mowers... well worth keeping and using.. :smile:KennyV