A coil spanner was an engineering tool with various uses. One variant of this technology was the interphasic coil spanner. (DS9: "Hard Time")
On Enterprise NX-01 in 2154, Lorian used a coil spanner to make adjustments to a plasma injector. (ENT: "E²")
In 2372, Lon Suder murdered fellow USS Voyager crewman Frank Darwin by striking him in the back of the head with a two-kilo coil spanner. (VOY: "Meld")
Chief O'Brien asked Worf to give him the coil spanner when he repaired a console in Ops. (DS9: "Bar Association")
On a salvage mission to Empok Nor in 2373, Boq'ta asked Amaro to retrieve a coil spanner so he could loosen a bolt. Amaro returned with a flux coupler instead, to find Boq'ta killed by a Cardassian soldier. (DS9: "Empok Nor")
In 2375, Ezri Dax used a coil spanner to tune a phase amplifier on AR-558. (DS9: "The Siege of AR-558")