In some designs it is very easy to replace portions of the deck in just a few minutes. In the bigger screens to replace just a portion takes time, with these decks a screen will be temporarily patched. Just putting a patch on does two things, first allows the repair to be done when it is convenient for everyone, mechanics and operating crew.  By coordinating other necessary work at the same time, the mechanical crew can make the most of down time needed to make the repair. A patch will also extend the life of the deck. Deck screen is expensive, this makes it very desirable to make it last as long as possible. When there is one point of high abrasion, replacing just that one area will allow the rest of the screen to be worn out before replacing the entire section.