bmp1.palette:=bmp2.palette - What happens?

Hi,

I'm using two 16bit-bitmaps and need the same transparent color.
Just using the same transparent color does not work, because both
bitmaps also need the same palette.
One of the bitmaps is very large the other is very small (just 2
lines).

There are two solutions which work:
  smallbitmap.assign(bigbitmap);
  smallbitmap.height:=2;
or
  smallbitmap.height:=2;
  smallbitmap.palette:=bigbitmap.palette;

I would prefer the second solution, because this prevents
bitmap.assign(), which would create a very big bitmap.
But what does  smallbitmap.palette:=bigbitmap.palette  really mean?
Will smallbitmap and bigbitmap share the same palette?
What could happen if I destroy one of these bitmaps?  

Volker Berninger