Rolling Walls and Ceilings

Rolling looks like the easy bit until you see the lap marks, the tram lines and a speckled floor.

The main rule is the one from cutting in, carried across a whole wall: wet paint must always meet wet paint. A wet edge is the still-workable edge of the patch you've just rolled. Roll the next patch into it while it's wet and the two merge into one film. Let it dry first and the overlap becomes a double layer that shows as a stripe of different sheen, a lap mark.

It's like ironing: keep the hot edge moving into the next bit, or it leaves a crease. So once you start a wall, finish it, working across from one corner, and save your breaks for the corners.