Old windows in house. Around the frame is coming apart so attempting to restore them. As part of that, does anyone know what this is actually called and would you replace it with cement, mastic or other? https://www.dropbox.com/s/iys93gxjwa0fjiq/IMG_20170806_114616.jpg?dl=0
Scrape all the lose cement off and use Toupret Touprelith 'F' Exterior Masonry Filler, very good product and available from Screwfix.