Which laboratory item would be used to file down rough edges of glassware?

A triangular file is specifically designed for smoothing and shaping materials, including glass. When glassware is cut or broken, it often leaves sharp, rough edges that can pose a safety hazard in laboratory settings. The triangular file has a pointed edge and a flat surface that can effectively grind down these edges, making the glassware safer to handle and use.

The other items listed serve different functions: a cork borer is used for cutting holes in softer materials, a measuring pipette is used to measure and transfer liquids accurately, and rubber stoppers are utilized to seal containers. None of these items would effectively address the issue of rough edges on glassware. The triangular file is the appropriate tool for this specific task, making it the correct choice.