The peak, or point of a roof is known as the ridge. When applying shingles on a roof, there are a special type of shingle called a ridge shingle that should be used. These shingles are typically a little thicker than normal shingles so they can withstand the bending without breaking or tearing.
Proper high quality ridge shingles also have extra adhesive to allow them to stay down more easily, and most come with a slight pre-bend at the angle of the ridge formed into them. They also have a thicker nailing area which helps prevent tears and rips.
Shown above is regular 3-tab shingles, which would normally be used for flat surfaces, installed on the ridge vent. Not only is this a lot of extra work for the installer, it is also highly likely that the shingles on the ridge will tear, rip, or leak before the rest of the roof.