A Pattern is an item that is used in autocrafting. It stores the recipe that should be autocrafted.
Hold SHIFT to see the output of the Pattern displayed on the item texture.
The Pattern can be configured to be a oredict pattern. Instead of extracting the exact item, it'll try to extract equivalent items according to the oredict as well.
When configured as a blocking mode pattern, this pattern will only allow to run autocrafting one-at-a-time.
Clearing a Pattern
Use SHIFT + right click in your inventory while holding the Pattern to clear it.
Modifying the Pattern
If the Pattern is a regular crafting pattern, one can modify it by re-inserting it into the output slot of the Pattern Grid.