Simple Inked allows you to setup your operators to only perform certain services. For example, if you have specialised tattoo artists, you can assign specific services to the more expert artists.
Go to your Operators tab in Admin and click the Services link next to an operator.
By default the operators can perform all services. Click Add Service to specify the services they can perform.
On the right side panel choose the Service Category and tick each service(s) which the operator can perform. Click Add once you've ticked all the services from each category.
Continue selecting the services until you have chosen all the services which the operator can perform. Do the same thing for all of your operators who can only perform specific services.