Correct Measuring of Moulding to Cut on Morso

[CreativePhotographer]

Hi there - I've had my morso and moulding sitting in my studio for a few weeks (due to other life pressures I haven't engaged with it properly) I am now ready to do so but am not really making sense of my notes for measuring etc

So.. I have a mounted image which is 250mmx250mm. As I understand it do I need to measure the width of the moulding (rebate)? and deduct this from my calculations. (I remember I need to take into account both ends of the moulding). I have a very helpful measuring system on my morso to the right hand side.
Can anyone recommend a clear, easy YouTube or similar so I can watch the process as this is how I learn best.
Thank you!

[JKX]

There are a couple of types of measuring scales, can you post a photo of yours.

There probably is a YouTube video but I’d have to search for it and I’m sure I’m no more capable of doing that than you are

[Gesso&Bole]

Your Morso is the De-Luxe so you don't have to do any calculations.

1) cut the first mitre on the moulding
2) slide the moulding to the right until the base of the moulding (touching the surface of the Morso) lines up with the measurement that you want. In this case, if your glass size is 250mm, you will want to look for 25 at the top of the scale, and follow the diagonal line down to where it meets the (inner) edge of the moulding. You will also want to add an allowance so that the glass will easily drop into the frame - most framers add 2mm., so you will actually want to measure 25.2cm/252mm.

[CreativePhotographer]

Thanks to both Jim and John for your help.
Anna