The Key and Lock Barrel kit comes with 2 metal keys with a plastic coated handle as well as 4 metal lock cores so you can lock up all 4 corners of your cross bars.
Installation is easy. The plastic lock cores just push out of the end covers. The metal lock barrel will have to have the keyed teeth facing the Modula name (center of the cover) and gently wiggle and push until its seated in the hole. Once this is done place the key in the barrel and try it out to see if it turns. If it doesn’t turn keep the key in the barrel and gently push the barrel out of the hole from the backside. Rotate it 90 degrees and try again until it turns without any issues.