A magnospanner was a type of engineering tool, used for adjusting the manifolds of 23rd century starships.
By the mid-24th century, magnospanners were rarely used, other than in Starfleet Academy instructional courses. (SCE eBook: Many Splendors)
Chief Miles O'Brien once used a magnospanner to repair Garak's shop door. (DS9 short story: "Broken Oaths")