Often times in slot canyons, you will need to travel up or down the canyon walls instead of just along the ground. Chimneying is the process of pinching yourself between the two walls. Chimneying is achieved by placing your back against one wall and your feet against the other wall. Your body will be facing sideways or up. Your hands are used for balance and for helping you move.
There are two basic movements options while chimneying.
The first is to keep both feet on the wall in front of you and to push off the back wall with your hands while you shift the position of your back.
The second movement is to keep one foot on the wall in front of you and the push off the back wall with your other foot while you shift the position of your back.
Situations where you would want to chimney.
The canyon bottom is too narrow to squeeze through.
The canyon bottom opens up into a silo or bombay.
You have to negotiate down a rock fall and don't want to waste time rappelling.
You want to avoid water or something else.
Chimneying is quite stable and requires less muscle strength and endurance than stemming or bridging.
When compared to walking or stemming, chimneying is slow. You are also limited in the width of canyon that you can chimney. You can't chimney across a canyon that is wider than the distance from your feet to your hips.