Here are four full adders chained together. These adders add two four-digit binary numbers (0 – 15), formed by the upper row of inputs and the lower row of inputs, resulting in the five digit binary number (which will always be ≤ 30) formed by the row of outputs at the bottom.
The carry-out of each adder connects to the carry-in of the next adder, forming the chain (as opposed to the single full-adder, where both the carry-in and the carry-out are directly drawn). The right-most adder is a simple half-adder, since there is no carry-in to incorporate. The carry-out from the left-most adder is drawn directly as the most significant digit of the output, since there is no further adder to carry to.