what kind of parts will be needed when assemble overhead trolley?

For a pair overhead trolley, need 2 bolts and nuts, 2 H-attachments or 1 I-attachment.                                                                                                       

For a load bar assembled, need 2 pairs overhead trolley, 4 bolts and nuts, 2 B-attachments, 2 spherical washer, 2 bushes, 2 castle nuts and 2 cotters.