General description The 300mm Multifunctional Protractor Combined Square Ruler is a versatile stainless steel measuring tool designed for professional carpenters. This tool allows for precise measurements and angles, making it an essential addition to any woodworking toolkit. Installation To achieve a 90-degree angle between the ruler and the handle, tighten the nut after aligning the top of the handle and the ruler parallel. To move the handle, first loosen the nut and remove it, allowing the handle to loosen with the ruler.