Gather your materials and print out the casing with the provided STL's. We recommend a stronger filament like PETg but a PLA should be fine if that's what you have on hand.
Cut the heads off of the brass nails and insert one into the end of the printed main body until at least 3mm protrudes into the well. Placing the nail into a cordless drill makes this step easier as it heats the plastic up a little which also provides some stability to prevent slipping after it cools back down
Place the LED in the provided slot with the positive lead pointed towards the brass nail. Trim the lead accordingly and solder to the brass nail.
Take the battery plate with the spring pinch locking tabs. With a pliers hold the battery plate and bend the soldering tab 90 degrees toward the spring. Trim resistor leads to 12mm, solder one resistor lead 90 degrees to the battery plate with spring
Cut 100mm of the 20 AWG stranded wire, strip 5mm of insulation off both ends. Then solder one end of the wire to the open lead of the resistor.
Slide the battery plate with spring into the negative plate slot provided in the plastic body. Then push the other end of wire into the hole at the bottom of the positive plate wall coaxing the wire into the channel. Solder this to the end of the wire and negative lead of the LED. Trim excess wire and LED lead.
Bend the solder tab of the positive battery plate 90 degrees away from the bump. Using another length of 20 AWG wire approximately 2 to 3 feet long, strip 5mm of insulation off both ends. Solder one end of wire to the positive battery plate. Make sure it’s in-line with the tab. With pliers, pinch down the locking tab of the positive battery plate and place the plate into its slot.
Run the wire through the hole in the wall of the body nearest the LED. Place a tie wrap on the wire at the inside wall to provide a strain relief, tying a knot in the wire also works.
Solder the other brass nail to the other end of the long wire and wrap the wire around the wire wrap on the exterior of the print.
Add the batteries and screw down the cover with the (4) M4 6mm button head screws. Now you can test your Continuity Tester!