Daggers
While fleeing from Providence, Rachel sees the mill that intimidates her. Presumably, the mill is for processing the cane grown on the plantation. The mill is intimidating because "its arms splayed out like for sharp-edged daggers making an angry cross into the sky." The sight of the dagger-like arms heightens Rachel's' terror. She is horrified, as if the mill is a person that could report her for fleeing from the plantation. The daggers denote the pain her masters would subject to her if she is caught running away.
Stone
Shearer likens the slave-owners' faces to stone. The metaphoric stone underscores their unhappiness. Shearer writes, "All the slaves of Providence had gathered outside the great house. A stone-faced set of white people waited for them." The white people were enraged that the Emancipation of slaves would deny them labor. They did not endorse it because it would make slave people free. They are insensitive to the utmost desire of the slaves, which is to regain their liberty.
Iron
Someone grips Rachel's hand when she is in the forest. The grip happens after she has been running for hours and is extremely fatigued. Shearer writes, "There was silence. The grip on her was like iron. Fear kept her limbs twisting in vain." At this moment, Mama B has found Rachel, who is too exhausted to keep running. Mamas B, together with another man, conclude that she is a runaway and take her to the tobacco plantation. The grip is lifesaving for Rachel.
