Hi Simon,
There is no direct option available in the Mechanical GUI. You can use APDL Command in the mechanical to select the different surfaces.
Follow this attached documentation to do it.
https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v231/en/ans_cmd/Hlp_C_SFE.html
https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v231/en/ans_elem/Hlp_E_SHELL131.html
Regards,
Sampat
You are navigating away from the AIS Discovery experience