You use your fingers and a stone to begin cultivation of the land. You use your fingers to till the soil, the stone to flatten the ground, and you carefully poke the seeds into the dirt and then use the stone to smash them further down.
Cultivation is suddenly halted because a tack (たく) sticks into your finger. You pull the tack out, throw it away and start cultivation again when... ouch! There's another tack. This field is full of tacks!