Place your scrap cardboard on a smooth surface and draw a perfect triangle on it with the help of the straight edge of the ruler. Keep the height of the triangle according to your choice, keeping the height of the zigzag cuts in mind.
Grab a sharp scissor and cut out the triangle carefully.
Now, place your ripped pair of jeans on a flat surface and remove all its wrinkles with your hands so that you can get a clear idea where to cut it from. Take a medium or large sharp scissor and cut your old jeans into short, keeping your desired length in mind.
Note: They best idea is just wear the old jeans, identify the exact length that you want to keep and mark it with a marker or pen. Then take it off and cut along the marked area.
Set the extra pieces of the jeans aside and set the short right in front of you.
Now it is the time to give it a zigzag look. Place the triangle cutout on the bottom edge of your short and carefully draw an outline with the help of a lead pencil.
Now, keep on tracing along the edge of the short, and on the back side as well.
Go through step 5 on the other leg.
Cautiously cut out along the outlines on right leg and then repeat it on the left leg.
Your beautiful Zigzag short is all set to go.