Riddle 62

I am hard and sharp,
of entrance strong,
of departure strenuous,
to my master faithful.
I go under the belly,
and for myself a way,
direct I clear.
The man is in haste
who urges me
lingering behind.
A man with his garment
sometimes draws me out
hot from a hole ;
sometimes retreats into
a narrow space, I know not where,
violently compels
the southern man.
Say what I am call'd.