The speaker remembers meeting a compass in second grade and being struck by how strange it was. The image of a "headless ballerina with one wooden leg" is both funny and a little unsettling, and the speaker doubts that something so lopsided should be trusted with drawing perfect circles. The pinhole at the center bothers them too, a "seed for a stone," a hole where nothing can grow.
From there the poem turns to a different idea of how a circle should be made: from the outside, like a potter's wheel, or like hawks circling on a rising current of air with only tiny shifts of the wingtips. The speaker wonders whether humans, descended from tree-dwellers, could draw circles freehand if the mind simply emptied out.
The mood is playful, curious, and a bit stubborn. The ending is a gentle reversal: give the compass its missing leg back, and it becomes a gnomon, a sundial's pointer, standing still while the sun draws the circle around it.