I literally use this thing everyday. It is hella useful for every fixing job.

Simply put it on your index finger and locate the button in order to be able to press it with your thumb, done.

Now when you are in the middle of a tricky job and light is requiered, simply press the button and you are illuminated.

You need the following to build this thing:

LED, 3mm diameter https://www.banggood.com/375pcs-3MM-5MM-LED-Light-emitting-Diode-Beads-Resistance-Lights-Kits-Bulb-Lamp-p-1027601.html?rmmds=search&cur_warehouse=CN

Battery, 3.7V, 150mAh Lipo https://www.banggood.com/3_7V-150mAh-Lipo-Battery-for-Cheerson-CX-10W-CX10W-RC-Quadcopter-p-1050066.html?rmmds=myorder&cur_warehouse=CN

Big IO Buttons https://www.banggood.com/140pcs-14-Types-Momentary-Tact-Tactile-Push-Button-Switch-SMD-Assortment-Kit-Set-p-1018684.html?rmmds=myorder&cur_warehouse=CN