Build in a bag
Build in a bag is a type of challenge in which fans attempt to build a particular set without removing it from the bag in which it was originally packed or in which it has been re-packed. This can be a timed race or simply an individual test of skill.
These challenges are usually done with small sets and were first done with polybag sets.
Due to the fragile nature of the plastic bags in which sets are packaged, fans who enjoy this type of challenge have taken to placing the elements in more durable zip-loc-style bags.