Frame Clamp for stretcher bars. Rotates 360 without having to loosen any knobs. Interchangeable with System 4 base stands. System 4: The Ultimate Needlework Holder A complete Needlework System that provides for unsurpassed comfort and technique. All products are adjustable, rotate 360 degrees and are extremely easy to use, versatile, lightweight and portable. The majority of Needlework System 4  components can be mixed and matched. This means that you can build a custom system by choosing the type of stand (base) you would like to work on and then choose the type of needlework holder you prefer.