how to create a smaller inside outline of a shape

[Sushimonger]

I am trying to create an "inside border" to a complex shape.  Because it has many different tabs and recesses, I cannot simple copy the shape and shrink it.

If I make a copy, and then increase the stroke to 15 pt, the inside of that shape would work. But I don't know how to create an "inside outline" of that shape, or tranform it into a shape by itself.  Can anyone help me?

[SJRiegel · Accepted solution]

Object > Path > Offset Path

Enter a negative number to have the second path inside the first.

[Sushimonger]

thank you!!!