Hi Ellen,
You can select 'cm' as the unit in the grid configuration dialog. whether this does exactly the right thing is something you'll have to check yourself.
(personally, I would look at the pixel width and height, and divide them by 3. I'm not used to working in cm.)

The grid configuration dialog is found in the Image menu (Image->Configure Grid).

On Sun, Jul 13, 2008 at 4:26 AM, wrote:

Hi,

I am trying to make 10 cm and 20 cm horizontal and vertical lines on a photo. In other word, trying to divide a photo into thirds. Can someone help? Thanks.

Ellen

Quoting cabrio531@aol.com:

I am trying to make 10 cm and 20 cm horizontal and vertical lines on a photo.? In other word, trying to divide a photo into thirds. Can someone help?? Thanks.

I wrote a Script-fu a while back which will create a 3x3 grid layer based upon the dimensions of either the current layer or the image. The grid is created on a new layer so you can remove it or hide as necessary.

The command is added to the menus under "Filters->Render-Pattern->Rule of thirds grid" and the code for the script is located at the following URL:
http://flashingtwelve.brickfilms.com/GIMP/Scripts/thirds-rule-grid.scm

On Sat, 12 Jul 2008 14:56:19 -0400 cabrio531@aol.com wrote:

Hi,

I am trying to make 10 cm and 20 cm horizontal and vertical lines on a photo.? In other word, trying to divide a photo into thirds. Can someone help?? Thanks.

Ellen

Does Filters->Web->Slice help?

Owen