2. After determining the mounting location, remove the plastic plate and adjust the size of the plastic plate according to the size of the vent. The plastic sheet will usually have some edges reserved for cutting, which can be done with a tool such as scissors or a small saw to ensure that the plastic sheet matches the size of the vent.
3. Apply an amount of glue or double-sided tape to the edges of the plastic sheet and fit the plastic sheet tightly against the edges of the vent. Make sure the plastic sheet is flat and not wrinkled or loose. 4. Wait for the glue or double-sided tape to dry and set, then check to see if the plastic sheet is securely fastened to the vent. You can gently tap or shake the plastic sheet to make sure it is securely fastened and not loose.