An ordinary garden hose can also be used to open some drains. Insert the end of the hose as far as possible into the drain opening, and pack wet rags around the hose to keep water from squirting out. Hold the hose in the drain, and have someone turn on the water to the hose for a few seconds. Use short bursts of water to create sudden jolts of pressure. This is a flexible cable, sold at most home centers and plumbing-supply outlets, that is inserted into drain openings to snag or break up drain clogs.
Special snakes are available for toilets.
It may be necessary to remove sink traps or other fittings in order to get a snake deep into a drain. Chemical drain cleaners are useful in some situations, but my personal rule is to never use them unless a drain is at least partially open. The best use of chemical drain cleaners is in maintenance. Occasional use in a troublesome drain can help prevent serious clogs.