A container sealing apparatus is provided, comprising a sealing tool having a lower tool half and an upper tool half; a feed lane for transferring one or more containers to and away from means for transferring containers on to the lower tool half of the sealing tool; and a lifting mechanism for moving the lower tool half towards the upper tool half. The container sealing apparatus also comprises an elongate container guide extending along the feed lane and sealing tool to laterally locate containers as they are transported along the teed lane and sealing tool, and control apparatus adapted to adjust the lateral position of at least the part of said container guide extending along said feed lane.