These test loads have jumper terminals to select the number or diodes, 1-10, you want to use or simulate a specific voltage drop. Now, for some people who are wondering what is a test load/dummy load and why do we need it? A test load or dummy load acts like or simulates a laser diode to safely measure how much current is going through it from the driver. Without one you run the risk of destroying or damaging the laser diode.
NOTE #1: These diodes are safely rated up to 3A, but at higher currents (more than 1A) they will get hot. I would advise less than 1 minute cycles for high currents or if you want you could place a small heat sink on top of these diodes and or resistor to help cool the test load if you plan on using these for more than 1 minute. Easy to find small heat sinks at RadioShack, DX, or you can source your own.
NOTE #2: If the driver you are using has a capacitor (most likely), you need to discharge the capacitor using a resistor before connecting it to the actual laser diode to prevent voltage spikes that might kill it or damage it.
NOTE #3: If you need help building the kit, I have instructions you can follow here: *How to Assemble the Selectable Test Load*