To hold or clamp wireline / slickline at surface during fishing operations.
Extract Allen Cap Screws from the top and bottom plates so the clamp be separated into two parts.
Ensure the proper sized inserts are installed into the clamp before installing around the line.
Install around the line, ensuring the slickline / wireline is aligned in the centre of the inserts. Install the allen cap screws into the top and bottom plates and tighten. This will hold the line stationary.