MarkS, I'm not sure what 'tamping a frog' refers to ,but I know that frogs are used to re-rail a de-railed engine or car truck [set of wheels]. Why Gandy dancers would be doing that is beyond me as Gandy dancers were the crews that realigned the rails; a task that was done by hand with 'tamp bars' [originally made by The Gandy Co.] The work was done to rythmical singing and became known as Gandy Dancing. I am not familiar enough with railroading procedures to know any other place that frogs would be used other than for re-railing a de-rail.