How are these sharpeners?

[afultz075]

Found an old sharpener in my drawer. It's older but appears to be in great shape. I'm thinking of putting this one in my car for sharpening when out and about if I need. I'm just wondering if these type of sharpeners are any good? I won't use it if it's a piece of junk that will do more harm than good.

 

[yoda4561]

Trash, maybe handy for field sharpening machetes, not much else.

 

[Old CW4]

Please do NOT use this device on anykind of even remotely good knife. Keep for mower blades, hoes, etc. only. Use on a knife only if it's for someone you dislike.