Knock4 is an interest-based social network which allows its users to explore their interests on and off-line in a social environment. By using Knock4, people can immerse themselves in their interests and find out how those interests are facilitated in their area. A simple, yet powerful recommendation engine brings users other people, venues, groups, events and interests that they may not have even considered before, whilst a comprehensive search and filtering feature allows users to find these things locally, helping them to explore their surroundings off-line, whilst dedicated interest pages allow them to discuss and further their hobbies on-line. Best of all, it's completely free!