Shield goes in the off-hand slot , which is slot 17 in WoW TBC.

Quick Scoop

In TBC, shields are equipped in the off-hand equipment slot, so if you’re using a macro, /equipslot 17 is the shield slot.

Useful note

That same slot is also used by many off-hand weapons, so a shield will replace whatever is currently equipped there.

Example

For a simple swap macro, you’d use something like:

text

/equipslot 17 Shield Name

That equips the shield into the off-hand slot.