When a square at one of the edges of the grid is filled, we can deduce that this square is part of the first (for left and top edges) or last (for bottom or right edges) blocks described by that line's clue.

This technique is sometimes called 'glue', as it can be thought of as pushing the block 'through' the filled block, extruding it to its final length.

A more advanced version of this technique is to apply it when the filled square is at a remove from the edge of the grid. As long as the block described in the clue is longer than the gap, we can conclude that the squares on the opposite side of the gap up to the total length of the block are filled.