Can Visual Guard .Net prevent a mechanic to be able to access any parts classed as 'Sales' modules?
The idea is to identify in your applications every object (form, control, link...) which is related to your "sales" module.
Then you create "hide" or "disable" permissions for all of them.
then, you gather all these permissions in a pemission set (for example "Mechanic permissions")
You create a role "mechanic" and you link it to the permission set "Mechanic permissions"
You create the user accounts for your mechanic guys, and grant them the role of "mechanic".