Copyright questions for patterns that use someone else's tools
I saw a gal on here who is selling her (adorable) shamrock pattern for use with the Twister ruler. I made an American flag with the Twister, where the pattern is a give away for our Shop Hop next month (I work at a quilt shop), and one of the employees wanted to buy it (before I told her it's going to be a give away). That plus all the discussions lately about copyrighting got me wondering - can you make a pattern that uses another copyright tool, for example the Twister, and sell it without infringing on the Twister company's copyright? Obviously I know I couldn't use the Twister's wording for the ruler's insert, but otherwise, would that be okay? "Here's a pattern, here's the layout, use the Twister to cut it up, sew back together - ta da!" Or could the Twister people issue a cease and desist and/or sue? How does that fit into the copyright discussion?