How do you cut a shower arm when the thread is to long?

To cut a shower arm that's too long, first turn off the water supply and remove the shower head. Use a pipe cutter or a hacksaw to carefully cut the shower arm to the desired length, ensuring a straight cut for a proper fit. After cutting, smooth any rough edges with sandpaper or a file. Finally, reattach the shower arm and the shower head, ensuring all connections are secure to prevent leaks.