Plug-assist techniques are adaptable both to vacuum forming and pressure forming techniques. The system shown in Fig. l2.4, is known as plug.assist vacuum forming in that a vacuum is drawn after the plug has reached its closed position to complete formation of the sheet. In plug-assist forming, the process differs in that after the plug enters the sheet, the air under the sheet is vented to the atmosphere. When the plug completes its stroke and seal the mold, air pressure is applied from the plug side (through the plug or from behind the plug).