Has anyone got a beam lying about that could measure something for me. I need to know the distance from drum face to drum face. The width in other words

Has anyone got a beam lying about that could measure something for me. I need to know the distance from drum face to drum face. The width in other words

I make it 1395mm face to face only checked one beam

Sorry should have said it didnt need to be mm accurate just a rough idea. Thanks for your help, have some mod rep