Shiptheory has introduced a new option for certain UPS services called Saturday Delivery, you can create rules and book shipments using this enhancement so that a shipment will be delivered on a Saturday. UPS Saturday Delivery is limited to what services are allowed this enhancement, I've listed below the services which allow this enhancement.

UPS Saturday Delivery is available for these services;
UPS Next Day Air Early
UPS Next Day Air
UPS 2nd Day Air
UPS Ground
UPS 3 Day Select
UPS Worldwide Express Plus
UPS Worldwide Express
UPS Worldwide Express Freight

Where do I find it?

There are two places where you can select this option, one is the rules UI and the other is when you're manually editing the shipment details.

The first picture shows where you'll come across UPS Saturday Delivery, within our shipping rules interface you have the option to create shipping rules that automatically book shipments with UPS Saturday Delivery, you just need to create the rule and click on the enhancements drop-down menu.

The picture on the right is what you should see when you want to book a shipment with Saturday Delivery enabled. You don't have to worry about booking a shipment with Saturday Delivery if you're service doesn't allow it because the option will only be made available for the services that do.

How will I know if a label has Saturday delivery?

If you're unsure whether or not a shipment has been booked with the Saturday Delivery enhancement, the easiest way to tell is by looking at the label, as highlighted in the picture below you should see a capital 'S' on the right-hand side of the label

If you have any questions about this please don't hesitate to contact support, we'll be more than happy to answer any queries you have.