An estimate leave signature message is what the customer will read and sign when an engineer leaves the premises. This can include any necessary information, disclaimers, or a simple acknowledgment of the engineer having attended the site.
In order to edit or create this, first go to your system settings. In the list of mobile settings click 'Estimate leave signature message'.
You will see a page with 2 choices. Click 'Yes' in order to set up this message. Then you will see a box where you can enter your message. When you are happy with this message click 'Save'.