Here’s how to root your HTC Evo 4G on HBOOT 2.18 with S-OFF!
Step 1. Check the Software number on your HTC Evo 4G. If you have 4.67.651.3 or later, this method will work. If you have an older version, try the easier root method, don’t need to do this.
Step 2. Take the battery out and back in. Then boot into bootloader by holding down Volume Down and Power button together.
Step 3. You should see that your phone says “LOCKED (OOW)”, HB