Notes on this puzzle
12 clues around the edge, out of a possible 28, frame this 7×7 grid. 6 heights are already standing inside the grid.
There is 1 clue of 1 around the frame; the first cell beside each of them must hold a 7. The bottom edge carries the most clues (4). 16 edge positions are blank, so parts of the grid are solved from the inside out.
Where to beginTry row 6, column 6 first: its row and column clues decide it without any other help. Use notes for the heights 6 and 7 first; once they are placed, the lower heights follow.