With the old Amstrad CPC computers you could connect 2 Amstrad joysticks to the computer by connecting the second joystick to the port on the first (there was only one port on the computer itself). This was fine if you had an Amstrad joystick.
If you happened to have non Amstrad joysticks (Kingston, Quickshot or Atart etc.) you were limited to one.
Below is a wiring diagram showing how to make a cable that allows you to connect two joysticks to the single port on the computer.
Wiring diagrams on this site are provided as is. I cannot be held responsible if you damage your equipment or yourself, either through errors in the wiring diagrams or through any errors that you may make when assembling the lead. Also remember that electricity (especially mains electricity) is dangerous. Take care when working with it.