The main tip for Level 815 is to use the line blasters (springs) to swipe the mesh machine twice in a row to destroy it.
If you are able, do it as soon as possible by dropping one line blaster level with the mesh machine, and the other line blaster in the row above above.
Set off the lower one first, then other straight after.
Next, line your bomb up with the remaining metal block to destroy it.
Then try to get the remainder of your blocks either cleared, or into the bottom row, where they can be caught by the final line blaster.