The chips are down

No theme for Tiny Tuesday so I thought this would do.  Despite appearances it's not a corrugated iron roof but it is very old; certainly as old as me and to be honest, I've no idea how much older.  Found in the kitchen, and probably a bit of an enigma to younger people; certainly not something they might think of using and they probably won't have experienced the shape of the thing it produces, although they will almost certainly have eaten it straight.

You may have guessed but if not it's the blade of a knife for cutting potatoes into crinkle-cut chips.  A very useful item; increases the surface area of each chip by quite an amount; I'm sure there's a mathematician out there who could give me a formula for how much.  Bigger surface area = more crispy chips!