All gaps are filled in by the red lattice. This lattice, together with this first row of pipes, is the pipe screen. Although you can't see behind the screen, the sound can still get out. The pipe screen is useful when the builder wants to hide the other parts of the organ which are not as attractive as the pipes. Many different materials for pipe screens have been used.
Most builders use wood carvings or metal shaped into intricate patterns.
I have even seen cloth but that is not a good screen because it muffles the sound. The pipe screen is there to make the organ attractive, not detract from the sound. The Dobson pipe screens are unique because they are pieces of painted PVC pipe with wood joining them together on the backs of the pieces. Pipe screens often use the first row of pipes, artistically arranged, as part of the screen. However, some builders will not use the front pipes to hide others and will put a large screen in front of the whole organ.