Based on the clue 'as a noun its the horny sheath covering the toes o...', what is the answer?

Based on the clue 'as a noun its part of a fastener used with a nut a...', what is the answer? Based on the clue 'as a noun its pieces for fastening as an adjective...', what is the answer? Based on the clue 'as a noun its seen on crowded freeways as a verb i...', what is the answer? Based on the clue 'as a noun its the cry of a rooster as a verb it me...', what is the answer? Based on the clue 'as a noun its the opening of a volcano in the eart...', what is the answer? Based on the clue 'as a noun its the person who is in charge of the m...', what is the answer? Based on the clue 'as a noun its the rear portion of an aircraft as a...', what is the answer? Based on the clue 'as a noun its the top layer of the earths surface ...', what is the answer?