Okay of course i checked the API and there is nothing - at least under this class name.
What i mean is the widget referred to as a bottom bar in the Apple Human Interface Guidline. Do i have to draw this myself from a NSView, if so how do i get the texture drawn?
P.S.: I added Toolbar to the tags because it is the closest generic keyword i can find and the bottom bar ist just the opposite as a toolbar.
You're looking for the "content border." This is something you need to set in code with Leopard, but you can set it in Interface Builder in Snow Leopard (note you must be targeting 10.6 or above in order for this to be a valid setting in Interface Builder).
You can conveniently set a large or small border (using the standard Apple-approved sizes). To set this, select your window in Interface Builder, then show the Size inspector. At the bottom of the panel, you'll find the Content Border settings.
Brandin Walkin's excellent BWToolkit (BSD license) provides support for UI in the content border (among many other nice UI elements) and makes using a "bottom bar" much more enjoyable.