How do I know if I have spring under or spring over?

When determining whether your trailer has a "spring under" or "spring over" setup for its leaf springs, you need to look at the positioning of the leaf springs in relation to the axle

In this setup, the leaf springs are mounted underneath the axle.

Identification: Look under your trailer. If the leaf springs are positioned below the axle, with the axle sitting directly on top of the springs, then you have a “spring under” configuration.
Example: Refer to the top part of the image where the leaf springs are shown underneath the axle, holding it up.

In this setup, the leaf springs are mounted above the axle.

Identification: Look under your trailer. If the leaf springs are positioned above the axle, with the axle hanging from the springs, then you have a “spring over” configuration.
Example: Refer to the bottom part of the image where the leaf springs are shown on top of the axle, with the axle suspended below them.