# n(b)/n(c) - Mask Definition
```
n(b) = { yappMaskDef } : If a yappMaskDef object is added it will be used as a mask
for the cutout.
n(c) = { [yappMaskDef, hOffset, vOffset, rotation] } : If a list for a mask is added
it will be used as a mask for the cutout. With the Rotation
and offsets applied. This can be used to fine tune the mask
placement within the opening.
```
There are several predefined masks or you can create your own custom mask definition.
The following are the predefined masks:
* maskHoneycomb
* maskHexCircles
* maskCircles
* maskBars
* maskOffsetBars
* maskSquares
To use a mask without modifiers **n(b)** you can simply list the mask name. For example **maskHoneycomb**.
maskHoneycomb
To use a mask with optional modifiers **n(c)** you can specify a vector (list enclosed in \[]'s) as follows:
```
[mask name, hOffset, vOffset, rotation]
mask Name = the masks name from the predefined list or a custom mask you have created.
hOffset = the distance in mm to shift the mask in the X axis (horizontal).
This will change how the mask aligns with the opening.
vOffset = the distance to shift it in the Y axis (Vertical)
rotation = the angle to rotate the mask in reference to the cutout.
```
for example **\[maskHoneycomb, 0, 3.3, 30]**. This will select the honeycomb shaped mask with a vertical offset of 3.3mm and rotated 30 degrees.
[maskHoneycomb, 0, 3.3, 30]
you can only use n(b) or n(c) on the same object.
see [Mask Definition](https://mrwheel-docs.gitbook.io/yappgenerator_en/advanced-options/mask-definitions) for how to create your own masks.
