Knowing how to cut a straight line is essential for most projects. Tim Carter demonstrates one technique for cutting a straight line with a circular saw. This will also work for a jig saw. With his tips, you'll have no problem getting that straight cut every time.
To get this straight cut, first clamp a framing square on a scarp wood piece. Use a pencil to draw a mark along the edge of the square. Do not remove the framing square yet. Take your circular saw and place the fence edge of the saw guide against the framing square and make a short cut. Remove the square and measure the distance between the cut and the pencil mark. This will provide the offset needed for achieving those straight cuts.
Now when your remodeling project calls for a nice straight cut, mark the board where the cut should be. Then make a second mark over the same distance that you measured in the test cut. Clamp the framing square on this second line. Place the edge of the circular saw (or jig saw) against the framing square and make your cut.
This results in a straight cut every time. Try it the next time your project requires a straight cut.