Hello @lmassa! Thanks for coming to the Community for help with this.  I'd love to explain how to customize service item assignments in TSheets. There are a couple of ways to do this. Let me outline them both:

1. Log into TSheets and go to Feature Add-ons, then select Custom Fields. 
2. Click on Service Items, and choose an item.
3. Clear users to unassign them from that item, or check each name individually to assign them.

The other way to do this is from the employee's profile:

1. Go to My Team and select the name of the user.
2. Select Custom fields and select the blue link under Items.
3. Clear items to unassign them from that team member, or check items to assign them. (Items that are assigned to all users in Featured Add Ons will be grayed out and must first be unassigned from Feature Add-ons >> Custom Fields.)

Here's the full article that goes over custom fields and how to manage them: Set up and manage custom fields in TSheets.

If you have any questions about this, please don't hesitate to reply to this post. We're all happy to help in any way we can!