A food preparation and delivery system can include a plurality of cooking units such as ovens, each containing one or more prepared, but partially or completely uncooked, food items. The sleeve is pivotally coupled to the shaft of the first part. In addition, means for releasably attaching the substrate to a support surface is also provided. A one-way air valve is fitted in the intake, and the guide tube has a through hole in its wall, and a slide block is fitted on the through hole to close it up. The single filament fineness of the black dope-dyed threads is thicker than that of the black-dyed threads.