From PackRat Recipe Wiki

The Bonus Draw is a feature in PackRat that replaced both Pop-ups and Vault Bonuses. A Bonus Draw is awarded while actively browsing, and appear to be awarded completely randomly. However, you can only have a maximum of 5 Bonus Draws waiting to be used at any point in time, so if you find yourself going an extended period of time without getting any Bonus Draws, check to make sure you don't already have 5. If you do have 5, then once you've gone to your pack and used at least one, you'll begin getting them again.

To use it, make sure that your pack is not full. Click on "Draw a Card" and you will be presented with 5 choices. One is always a credit amount, one is always a face-down draw card, often one will be a lock and the rest are face-up draw cards. Note that if you choose the face-down draw card, occasionally you'll draw a lock instead of a regular card.

is the icon that represents the Bonus Draw.