If you are s-on (OOW unlocked) on hboot 2.18 u can used fastboot to flash a recovery, you should be using Amon RA on the evo and not cwm or twrp. If you are on hboot 2.15/.16 you need to use revolutionary.io to achieve s-off and gain recovery and the flash SU and SU binaries. Any hboot prior to 2.16 you use unrevoked or one of its variants to get s-off. If you're hboot 2.18 s-on locked you use htcdev.com to unlock the bootloader from there you can use fastboot to flash recovery or you can follow captain throwbacks guide to downgrade your hboot to an earlier version and achieve s-off. With s-on unlocked you can do (almost) anything you can do with s-off except you won't be able to flash PC36IMG.zip files, which include recoveries, radio updates, splashscreens, and RUU files.
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