Answer:
Gets rid of bad ones, short and tall. Tightens when used, one size fits all.
Without a bridle, or a saddle, across a thing I ride a-straddle. And those I ride, by help of me, though almost blind, are made to see.
Late afternoons I often bathe. I'll soak in water piping hot. My essence goes through. My see through clothes. Used up am I - I've gone to pot.
What is bought by the yard by is worn by the foot?
The sun bakes them, The hand breaks them, The foot treads on them, And the mouth tastes them. What are they?