A 3mm laser-cut aluminium folded into a 50mm high x 70 mm wide foot - length for the Bundutop rails are 2020mm - long enough to pick up the strength present in the extruded sides of the tent. 
 
Brackets are pre-drilled to accept sealed head rivets. The kit includes rivets, and a tube of 221 automotive Sikka Flex adhesive sealant. Instructions available on this video.