Could anyone please identify this? I'm ok with wood and have been repairing some old sash windows. I need to replace this where I have knocked it off. I'll use a sealer onto the actual wood but wondered how to make this up. I've researched trowel mastic etc. But I think this may be just a cement or render type thing. It's quite brittle. Any advice or recipes gratefully received. I'm nervous about colour texture and adhesion! Thanks Martin