In your book, you mention the term "isolate" and indicate that it is a C4 concept (or call). However, callers have used it and the only time they have seemingly used it was in parallel waves to get us into "point to point" diamonds. However, what is its actual definition. The Galburt Glossary says that is is merely a "lockit" move but that doesn't seem correct to me. What is the actual definition? On p. 30 of your book, you really don't define it.