Set the height
As a guide start by affixing a timber strip to the wall. The piece of timber needs to be about 18x90mm. This is going to give you an accurate guide for positioning and fixing the cabinets, and will make it easier to hold them in place.
To find the correct position to put your timber strip, start by marking the wall at your desired height from the lowest point of the floor (based on a ceiling height of 2400mm or more). Using your spirit level to guide you, draw a straight line from this mark where you will be positioning the wall cabinets. This marking stands for the bottom edge of your wall cabinets, and is the place to put the top of your timber strip. This height will also ensure your wall cabinets align with any pantries used.
Fix the strip to the wall, using your spirit level to ensure it’s level with the marker. If you have plaster walls, be sure to fix it to the studs you’ve already marked out.