Trade Secret Touch-Up Marker Set. This set of 3 touch-up markers works on finished or bare wood. Trade Secret 3pc Touch-Up Marker Set provides for light, medium, dark cherry and mahogany finishes. These low-odor formula markers are free of toluol, MEK and hazardous chemicals found in other markers. The color does not shift when exposed to light. They can be used months or even years after damage has occurred. Applying the markers on top of other Trade Secret products is perfectly fine.