Precision mode lets you slow your brush strike and make a more controlled stroke in a defined area. 

Why would you want to use this? Adding fine detail to a feather, drawing the Afterfeather, the Rachis, or barbs, can be very helpful. You can also use this on fur or creating the veins in a flower petal, anything that takes a more precise or slowed detailed stroke.

First, you must assign Precision mode to a button on your Quick Keys, Pen or Tablet. 

[1] I'm setting Precision Mode to use with Rebelle 6.

[2] I'm going to have it assigned to my 3-Button pen.

[3] Using the lower switch. 

[4] Click on the button you are wanting to assign Precision Mode to.

[5] Select Tablet from the dropdown menu.

[6] Select Precision Mode from the list. 

When you press your lower Pen button, it will open Precision Mode, where your cursor is on your drawing.

[7] The lower button shows it is set to open Precision Mode when pressed.

Important to know that once you open Precision Mode, you will need to close it by pressing the lower button once more. 

[8] Once you open Precision Mode, you will only be able to draw in the highlighted box.

[9] The box size is not customizable. Once it is open, you will also notice that your pen movement is slowed. This is by design, as it will allow you to make fine and accurate lines on your drawing. 

Once you are down using Precision mode, press the button you have assigned it to, and the Precision box will go away, and you can draw on all areas of your canvas.