Hi Lisa,

Yes you can. 

As long as you don't enter a product/service on a line, you won't see a "zero".

I uploaded a pic as an example...but I'm not sure if it will show in my response. If it doesn't...just give it a try. 

If you can see the pic I uploaded...

You'll see I also used this "trick" (i.e. inserting a line without a product/service between other lines with products/services) to add "headings" (Materials and Labor in this example) in the Description area that describe the items directly below the "heading". I hope you can see the pic, because this description is getting very convoluted!