© B&Q's You Can Do It manual
Ensure the new worktop is the correct size. If replacing an old worktop you can use this as your template. Alternatively, if you are starting from scratch you will need to tailor the new surface to fit your space.
As walls are rarely completely straight, to achieve an even overhang at the front of your units, it may be necessary to scribe the surface if you have gaps against the wall larger than 4mm, as sealant won’t be able to disguise anything larger. In essence, scribing means cutting the worktop to the same shape as the wall, which will require cutting a line from the back of the surface to avoid any gaps against the wall. One way to do this is to measure the largest gap between the wall and work surface, then cut a piece of wood to the same depth as the gap. With the work surface against the wall, place this block flush against the wall with a pencil at the front of this block, then run the block and pencil along the top of the work surface to mark where you need to cut to ensure a neat fit.