You must find the seam in each strut. EMT is welded -- there is a seam
at the weld. You must locate this seam so that you can press the seam
at the right angle. If you do it wrong, you will split the strut at the
seam and the strut will be ruined (although, you might be able to cut the
ends off and make a shorter strut for some other purpose.)
You can find the seam most easily next to an end you have just ground. In other words, it can be hard to find the seam at the original ends of the 10' EMT. Look on the other end of each strut. Rotate it in bright light (or bright sunlight) to spot the seam. DO NOT TRY TO FIND THE SEAM ON THE OUTSIDE OF THE STRUT! There are lots of seam-like lines along the length of the outside, but only one on the inside.