NOOB RESOURCES: What are Appliers and What is Bakes on Mesh (BOM)?

First, please note that I only have experience with the Firestorm viewer, so if you use the SecondLife viewer, some of the menu options may be different for you.

NOTE: There are four items that your avatar will ALWAYS have to wear - these are your system skin, your shape, your brow shape, and your system eyes. These are the items that would appear on your system avi if you took off your mesh body. You cannot remove these; you can only Wear them (Add is greyed out). The icon for the system skin appears as a little human figure; the one for the shape is a greyish box with a human portrait inside it; the icon for the brow shape is a little mullet; and the icon for the system eyes is a pair of eyes.

This image explains what the various inventory icons represent.

What are Appliers and What is Bakes on Mesh (BOM)?

APPLIERS

Appliers are a HUD-driven process that "applies" a texture onto your mesh. If you have to use a HUD to click a button to wear a tattoo or makeup, that is an applier. In most instances, if you put on a lipstick using an applier, then use another applier to apply another lipstick, the first lipstick will be replaced by this new one. That said, some heads (LAQ for example), allows you to apply multiple layers of some makeup (i.e., to put eyeliner on your eye, then click a box to apply eyeshadow on another layer, etc.

Body and Head HUDs may have makeup, tattoo, and skin options and act as appliers. Some things - makeup, tattoos, etc., may have a separate applier. If the icon in your inventory appears as a small cube, then that is an applier.

BAKES ON MESH

Before there was mesh in SL, everything was essentially Bakes on Mesh. Clothing was worn, and there were several layers (undershirt, underwear/panties, pants, shirt, jacket, etc.). Just as in RL, underwear would appear underneath pants; an undershirt would appear underneath a shirt, and a shirt would appear underneath a jacket. Tattoos would appear underneath the undershirt or underwear layer.

Once mesh came along, we used appliers to apply tattoos and makeup. The addition of Bakes on Mesh (BOM) enabled us to add layers of items on top of our mesh bodies and heads. BOM items use the tattoo layer or universal layer, though some may also refer to the icons on the right side of the above image as BOM layers as well. Instead of clicking on a HUD to apply these to your face or body, you right-click the item in your inventory and select Add from the menu to add that layer to your face or body.

BOM opens up a whole lot of possibilities because you can use these textures on top of one another (up to 48 or 62 layers...I've seen both numbers, so I'm not sure which one is accurate). You could essentially add 20 layers of lipstick...if you wanted.

One thing to keep in mind with BOM, though, is that these layers will appear on top of one another in the order in which you add them to your face/body. An example of why this matters is that you would want to put freckles on top of the skin layer, but probably underneath your makeup layers. You might want to put pores and/or wrinkles underneath freckles. If you're looking to create a look with multiple eyeshadow shades, you might want to put them on top of one another in a particular order to get the effect you want. You definitely want to make sure your eyebrows are above your skin layer.

If you notice something wonky, try taking a layer off and putting it back on (it may just be underneath a layer you put on after it). If that doesn't work, see Why Did My Eyebrows Disappear below.  

BOM Tips

To avoid a line on your neck, when adding skins, add/wear the body skin first, then the head skin. Neck lines can also be dependent upon the EEP/Windlight settings you're using. If you have a line show up on your neck, your best bet is to reach out to the Groups for your particular head and body. 

Why Did My Eyebrows Disappear When I Added My New Skin?!

As stated above, the order in which you add things matters. You want your skin to be underneath all or most other layers. To move things up or down:

1. Right-click your avatar;
2. Select Appearance;
3. Select Edit Outfit;
4. Select layer that you want to move;
5. Use the arrows to move the item up or down.
6. Click Save, then close the window.

How to Tint Modifiable BOM Items:

1. Add item;
2. Right-click;
3. Select Edit;
4. Click Color/Tint square;
5. Select color;
6. Save