Hi Mary, if you're looking for a tool that was used in a specific post, you could go back to that post and pose your question in the comment area. Or, if it's a blogger post, you could follow the link to the blogger's page for more information. If you list the project here, perhaps we can help you track it down.
Hello Mary! I don't know what kind of banner you want to make but here is a link that has a printable pattern that you can use to cut out triangles for a banner made from material or paper.
Here are ideas for your banner
Here's a template that might work: http://www.mommysuite.com/diy-pennant-banner-w-free-pattern/
You could use one of the templates linked to, but if you cut out a lot of things, you might want to consider getting a die cutter like the Cricut or Sizzix Big Shot. You could cut out a lot of triangles all at once without a lot of effort.
what are you cutting that banner from ?
You could utilize one of the layouts connected to, however on the off chance that you cut out a great deal of things, you should consider getting a pass on shaper like the Cricut or Sizzix Big Shot. You could remove a great deal of triangles at the same time without a ton of exertion. you can find more by click here
How large is the banner, or what size do you want the triangles to be?
Make a template the size you want and layer up your fabric and then use a sharp strong pair of shears (Dressmakers) to cut a number at one time. Hope that helps