Nibal,
Of course, we have several articles put together to cover different scenarios and uses for Caps, and how they work. I simply searched the work "Cap" from the documentation section and came across the following four links. Please take a look through these links and let us know if you have any other questions about their uses and how they work.

Adding & Placing Auxiliary Equipment
Planning for Future Expansion
Adding to Existing Irrigation Systems
Size the Mainline Manually Using Caps