[Gimp-user] Alignment tool - Relative to Active path How does it work?

[Gunold Brunbauer <gunoldbrunbauer online de>]

I made a path and I clicked on the alignment tool with these settings: 
Relative to: Active path.
I clicked on a layer in my picture and I clicked "Align middle of 
target" -  but nothing happened.
Can anybody explain how to use this tool in the correct way.
I can find any clue in the context help.
Thanxs
G. Brunbauer