This tool is called a straightedge guide (also known as a positioning slider or line‑limiting block), and it’s a precision positioning tool commonly used in woodworking and DIY crafts. Here’s a detailed overview:

Core Functions

Precision Positioning: The guide can slide along the straightedge and lock into place at any desired scale, eliminating misalignment that often occurs when aligning scales manually and ensuring consistent line dimensions every time.

Parallel Line Drawing: Simply rest the guide against the edge of your workpiece and slide it along the straightedge to draw lines that run parallel to the edge—perfect for tasks like marking mortise and tenon joints in woodworking or pre‑cutting markings on sheet materials.

Repetitive Marking: Once the desired dimension is set, you can quickly create multiple marks spaced evenly apart, significantly boosting both the efficiency and accuracy of your line‑drawing process.

How to Use

Installation & Fixation: Slide the stainless steel straightedge through the guide’s slot and adjust it to the required length by sliding it to the corresponding scale mark.

Secure Alignment: Press the side of the guide firmly against the edge of your workpiece, ensuring that the straightedge remains parallel to the workpiece’s edge.

Smooth Line Drawing: Use a pencil or scribing tool to glide steadily along the edge of the straightedge—resulting in crisp, precise lines every time.

Applicable Scenarios

Cutting and marking sheet materials in woodworking projects; positioning mortise and tenon joints

Setting scale marks and drawing parallel lines during DIY crafting

Model building, leatherworking, and other applications that demand highly accurate line drawing