Cue Bid - Strength Showing
A Strength-Showing Cue Bid is normally used only when no other bid is available to show both the shape and strength of a hand.
For example, after 1-(1)-??, here are bids you could make with various 13-HCP hands:
Axxx-KQx-xxx-Axx - Double (take-out)
The last hand does not qualify for any of the other bids, so we make a general Strength-Showing Cue Bid of 2.