Question: what is the purpose of a carriage bolt
[{'answer': 'to fasten metal to wood', 'provenance': [{'wikipedia_id': '16256926', 'title': 'Carriage bolt', 'start_paragraph_id': 1, 'start_character': 82, 'end_paragraph_id': 1, 'end_character': 105, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '16256926', 'title': 'Carriage bolt', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 105, 'bleu_score': 0.910879922930628, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8647621857424435590}, 'section': 'Section::::Abstract.'}]}]