Step 1. Draw around a circular object (e.g. a plate or paint can) to make a paper template and stencil. Cut the stencil using a craft knife (make three and the job will be much quicker and easier).
Step 2. Use your tape measure and templates in place and line up the stencil over the first spirit level to mark the height of the first line on which the circles will sit – do this at both ends of the wall.
Step 3. Pull a wall-length piece of string over a stick of coloured chalk, tie a knot at one end and secure to the mark on the wall with masking tape. Pull the string across to line up with the mark at the other end. Pull tight against the wall and snap against the surface. Now you have a straight line to follow.
Step 4. Use the paper circle templates and a bit of masking tape to position the circles on top of the line. Evenly space them with about a 3cm gap between each circle, or juggle the spacing by eye to suit your wall.
Step 5. Once you have all the templates in place, line up the stencil over the first template and then lift it away, leaving the stencil in position. Hold the stencil in place with masking tape.