Just to add to what StangeRanger posted, you must have missed this on the main page.
"While the boards are mainly intended for information exchange, there are instances when an individual may wish to post something for sale to other collectors on the individual forums. If you wish to post an item for sale, you must be at least listed an “RKI Member.” You may also post items for sale if you are listed as a “Long Time RKI Member,” “Respected Member,” “Technical Expert,” “Industry Expert,” or if you are a Board Moderator."