Tdskip,
The attachment bolt is a 1" long 5/16" diameter bolt. Click on the attachment for a picture. The picture is of the driverside outside attachment. The seat back portion of the attachment is threaded for 5/16" fine threads so the bolt must go in from the inside. There is a washer between the seat back frame and bottom frame portion. Then there is a nut on the outside that acts as a jam nut. Hope this helps and have a good day!
John