Description
A singular RCA adder of one of many designs. Includes inputs A and B, CIN, and COUT. CIN is the side input, COUT is the two-colored 4-long wire, and A and B are the levers at the back.
RCA adder designs are great for redstone beginners - they are simple to explain, build, and use.
However, there is a drawback: RCA has a delay for each adder you add. Each adder has to wait for the last to finish. That is where 'Ripple Carry Adder' gets it's name. It ripples.
This means that not every calculation will take the same amount of time, and thus RCA is not recommended for applications with sensitive timings. If you do plan to use it in something with a clock, like a CPU, probably ensure that the clock is slow, as to give the RCA time. And for pipelined CPUs? Forget it.
Related Schematics

Bow auto crafter
Auto crafter for bow. The input chest can be inverted depending of the initial state of the T flip flop. It can stop working when missing one or multiple ressources without breaking and restarting without any clearance needed. I don't recommend to modify any item when they are in the droppers/crafter to prevent any desync.

16-bit Double Density(DD) CCA
DD Diagonal CCA. Inputs, located on the underside, are paired and alternate left to right (A0 B0 on the left... A1 B1 on the right... and so on) 4-ticks16-bit

8b vertical decoder
Generated by https://github.com/ZpippoZ/minecraft-vertical-decoder-generator