You're looking for a downloadable PDF of "The Key" by Wren and Martin, a popular English grammar and composition book. Here's some information and a possible download link:
"The Key" by Wren and Martin is a comprehensive guide to English grammar and composition. The book is designed to help students improve their understanding of English grammar, vocabulary, and composition skills. It's a widely used textbook in many schools and colleges. key book of wren and martin free download pdf