If you need to remove a chain that does not have a master link, you'll need a chain-breaking tool to separate a link. If you do not have the tool and need to get the chain off as soon as possible, you can temporarily break the chain with a homemade chain breaker, using tools that every gear head will have. If after examining the chain you find that it uses rivets to connect each link, you will need to have a chain tool that can insert and seal chain rivets if you need to reconnect the chain. For the breakdown process, or to break down and reconnect pin-style chains, a homemade breaker tool works well.
Place the block of wood behind the chain link section you're looking to separate, so one link end faces the wood and the other link end faces you. The wood will provide a cushion for the hammer blows and give the link pin a place to go, without damaging the workbench or the area around the chain, while supporting the chain. Place a socket with a larger centre hole between the chain and the wood. The will act as a spacer for the pin to enter.
Center the awl, a tool normally used to create a pilot hole for drilling on hardwood or metal, over the link pin you want to push out.
Hammer the awl onto the link pin, driving the pin through the back side of the link. Continue to tap the awl with the hammer until the pin is nearly pushed through the back side of the link. This will allow you to disconnect the chain links while keeping the pin partially installed, making reconnection an easy process.