"Yong Huang" wrote

Our carpet is 7 years old. It's quite dirty on the stairs especially
near the edge of each riser. I'd like to hear some good tips about how
to clean this part. I'm thinking of renting a steam vacuum cleaner

If you have a need for fairly frequent spot cleaning, consider getting one
of the smaller hand held units. 'Green Machine' I seem to recall is the
name. Folks with pets use them for the occasional 'oops' and they work
pretty well for that.

Very useful for stairs. Not super powerful, but they will work with a few
treatments and not too hard or heavy to get around odd spots. You can also
use them to clean the carpet in a car.

See if your friend has one you can borrow? Then you could try it out (buy
him a bottle of cleaner sold at just about any grocery etc).

One warning, they also come in a cordless style but those do not have enough
power to be of any use.