sole

Any of various chiefly marine flatfishes of the family Soleidae, having both eyes on the right side of the body, and including food fishes such as the Dover sole of the Atlantic Ocean.

Any of various other flatfishes, especially certain flounders.

The underside of the foot.

The underside of a shoe or boot, often excluding the heel.

The part on which something else rests while in a vertical position, especially.

The bottom surface of a plow.

The bottom surface of the head of a golf club.

To furnish (a shoe or boot) with a sole.

To put the sole of (a golf club) on the ground, as in preparing to make a stroke.

Being the only one.