Zigzag elbows or offset elbows are elbows that turn onto to 2 directions. For example, on a standard gutter situation, where the gutter is mounted to a fascia that protrudes
from the wall, an outlet would also be a few inches from the wall, and since a downspout is close to the wall, 2 elbows are needed. One carries the water from the outlet to the wall,
while the second ones brings it down to the downspout. Another example would be a ledge, where a downspout needs to come off the wall then straight down.
An offset elbow is simply these 2 elbows combined into a single piece. Such elbows are available as a custom order.