Castle of Elite - Official game guide|
Introduction - Basics - Solutions - Secrets - Trivia
When the guide tells you to place a brick symbol on a certain square, it means you should aim the mouse cursor on that square.
3-4: Trundler's adventure
A, B: Destroy these bricks. Wait for the Trundler to hit the yellow switch.
C: Destroy this brick. Wait for the Trundler to hit the blue switch.
D: Destroy this brick. Wait for the Trundler to hit the green switch. Now drop down to the bottom, and use a teleporter to get the symbol. Destroy E.
F: Stand here. Place the symbol on A.
G, H: Destroy these bricks. The Trundler will now press the last blue switch, opening the way to the goal.