Abstract: A wrapper to be wrapped around a stack of disc-like tablets includes a portion carrying a layer of heat-activatable adhesive, which is activated just prior to wrapping the wrapper around the stack to secure it in position on the stack. The heat activation is provided by a short, hot blast of air directed onto a surface of the wrapper opposite that on which the heat-activatable layer is located, whereby the applied heat must travel through a portion of the wrapper to reach the adhesive layer and activate it. The air blast is heated by heaters which include elongated heat exchangers having rectangular grooves or slots extending along the length of their outer surfaces, through which grooves the air blast is constrained to travel for efficient, rapid heating.