Make sure all of your shutters are completely pulled out. Shutters are metal slats that are used in focusing in order to cut off part of the light so it doesn't spill onto walls or scenery. There are four shutters on a leko, and they are located between the lamp and the lens tube. If all four shutters are pushed all the way in, no light will get through. Because lekos are often stored with all of the shutters in, you have to make sure all the shutters are pulled out.
Each shutter has a round, rubber grip on it. Gently pull it away from the body of the leko until you can't pull it anymore.
Turn on your light. If you are using a light board, make sure the appropriate channel is on. If you are plugged into a wall outlet, make sure your connection is secure.
Once your leko has power, your lighting designer may ask you to "flag" it. This means wave your hand in front of the beam of light so he or she can see what your instrument is lighting.
Point the light at the appropriate spot on the stage. Most lekos have a large knob on the yoke (the U-shaped bar that connects the lighting instrument to the C-clamp). You can loosen this by hand and move the leko up or down. To move the instrument left or right, use your wrench to loosen the small nut at the bottom of the C-clamp.
Once your beam of light is where you want it, you need to retighten everything. This is called "locking," because you don't want to have your instruments slipping out of place.
Fun Fact: The tiny nut is called a "knucklebuster" because wrenches often slip off of it due to over tightening. Sometimes it is referred to as the "Jesus Nut" for what is said after your knuckle gets busted.
Look at the pool of light on the stage. You'll notice that the center part is a little brighter. This is called a hot spot. Every designer is a little different, but most will want the hot spot to hit from the waist up if you are focusing on an actor.
Fine tune the light. You may have to do either a HARD or a SOFT focus. On the top of your barrel, or lens tube, is a small nut. By loosening this nut, you can slide the lens back and forth. When you do this, look at the pool of light on the stage.
When you can clearly see a sharp, defined edge to the circle of light, this is called a hard focus. This is often used for spotlighting a particular person on stage.
When the edges of the circle are fuzzy, this is a soft focus. This is often used when a designer wants an even wash of light across the stage,
When you have the focus you want, tighten the knob back into place.
Close shutters if necessary. Sometimes your light is spilling off the stage and into the audience or onto the curtains. The audience doesn't like light in their eyes. In order to fix this, you can close some of the shutters you opened before.
Because of the mirrored reflector in the leko, the shutters work opposite to the way you might expect. For example, if the LEFT side of the light is spilling onto a curtain, then you need to close the RIGHT shutter. If the BOTTOM of your light is going into the audience, then you cut it off by closing the TOP shutter.
Add a gel or a gobo. Gels are colored sheets that go in the front of a leko to change the color of the light. They are called this because they were once made out of gelatin. Now they are made out of synthetic material.
Put your gel in a gel frame. This is a square made out of cardboard or metal. Open up the metal clip at the front of the leko, slide in your frame, and then close up the clip to secure the gel.
Gobos, or templates, are thin circles of metal that have patterns stamped out of them. You can use them to project distinct images in hard focus, or create shadows in soft focus.
Gobos go in a gobo holder, which slides into a slot in the leko in front of the shutters. Remember, the gobo will be projected upside down to the way you put it in, so put it in accordingly.