[Chimera-users] Question from PhD student

Dear Chimera, I would like to know exactly how to enclose my EM density map within a cube of specified size (where x, y and z have equal dimensions, i.e x,y,z = 150 pixels). It seems that when I place a marker (from volume tracer) on my map and then specify the padding number a rectangular cube is produced instead. I there a simple command to do this or can it be done from the GUI? Many thanks T.I PhD student, London