DIY Potato Slicer

Place a bottle cap, bottom up, on a solid surface and begin flattening the edges with a hammer. Strike every point along the edge until it lies mostly flat, turn the cap over and strike its entire surface until it is perfectly flattened.

Punch two holes near the center of the cap by driving a small nail through with a hammer. Work slowly, striking the nail a few times, turning the cap over and continuing on the other side until the holes are complete.

Sharpen the edges of the cap on a knife-sharpening block. Hold the cap at an angle and run its edge lengthwise along the surface of the block, slowly rotating the cap's position to sharpen the entire perimeter. Work cautiously to avoid cutting yourself.

Cut a yard of string and thread it through the holes, creating a loop on one side of the cap. Tie the free ends together to complete a loop on the other side. Slide the cap until both loops are of equal size.

Hold the strings by the loops and move your hands in a forward rotation, twisting the string. Bring the blade into contact with a potato while pulling outward on the loops, causing the string to unwind and the blade to rotate rapidly, slicing the potato.