Same-day appointments can be enabled through the docks tab. 

1. Go to the Warehouses tab
2. Select a Dock
3. Make sure the Dock is available for carrier scheduling 
4. Change the number of hours on the first option accordingly 
5. Click "Save Dock" at the end 

How does it work? 
To ensure better planning for your warehouse, you can set a minimum notice time for carrier appointments. For instance, if you set it to "6" hours, carriers would need to schedule appointments at least 6 hours in advance. This means, if they want a 10 AM appointment, they'd need to book it no later than 4 AM. This way, your warehouse gets ample notice before appointments, avoiding last-minute surprises.