hi! I would like to know how i can mirror a subtool, like a hand … 
then if i modify the subtool, these modifications affects the mirror object?
Thanks!
Download Subtool master (http://www.pixologic.com/zbrush/downloadcenter/). Then use the the mirror function and select merge into the same subtool. As long as you work with symmetry on, you will get mirrored changes in the subtool. If you loose symmetry, mask the good one and use “Smart Resym” (deformations tab in the tool pallet) to get it back. If you really mess up, hide the messed up one, use “delete hidden” and then use subtoolmaster to create a fresh mirror copy of the “good one”.
-K
Thanks kerwin, always the right answer:D