Knockdown refers to models CKD-8.5, CKD-10 and CKD-12, which are descendents of former KTI (Kaul-tronics) antenna models, which SAMI manufactured under contract during KTI's last months of operation, and continue to make under their own brand name.
The knockdown style may be a bit more difficult to put together, but is a far better antenna in terms of being able to ship in a smaller package with less expense in freight charges. Not being pre-assembled minimizes the danger of damage in shipment common to four-panel antenna sections. We no longer sell the four piece design for this very reason---too many freight claims caused by rough handling, including spearing by fork lift tongs. Those considering knockdown versus sectional should also consider the eventual need to replace parts. If you try to repair a sectional antenna, it involves a tricky procedure of drilling out or otherwise removing the preassembled screws, and installing new mesh pieces to replace a damaged section. This is not always mechanically sound, because of the larger hole remaining when you get done---your choices to make a better mechanical connection include the use of Lock-Tite, a larger sheet metal screw, or to drill a new hole. If you have to replace an entire quarter panel, it ships in a huge box that is NOT shippable via UPS due to dimensional limits, and is therefore required to be sent via Motor Freight---usually with a high minimum shipment charge that can be close to the same price to ship an entire antenna.
The alternative is the CKD knockdown series. Individual panels can be purchased (rolled up in a small package that even the Post Office will ship) and shipped cheaply. Or you can cut the same from a rectangle of mesh that is shipped via a similar method and cost. Only the damaged panel needs to be removed from the antenna, and carefully replaced---meaning a much easier and cheaper repair job should the occasion arise.
