On any of the straight smokestack 4-6-0 locos you'll find a decorative cap on top of the stack. On some of my locos this is just slipped in, on others it is glued. If not glued, remove and follow step 2 below. This decorative cap can be used even after the cut (without the "Beartrap").

1. If the decorative cap is glued on the stack this means we'll be very careful in making our cut on the stack (especially, if you wish to use the cap again, later). Below the decorative cap is a ridge or rim, which is an integral part of the smokestack. The cut is made just below this rim, using the rim as a cutting guide. The cutting depth is approx. 1/8". If you don't wish to use the decorative cap sometime later, then the cut doesn't need to be made circumscribing the stack, you could just cut straight through the stack. However, I believe your cut will be more accurate cutting around the stack. Once the cut is made (to the point where the cap is loose) and you want to use the cap later, then the bonded plastic on the cap needs to be removed. This is done by removing small portions at a time until the cap is clean and can be re-plugged into the stack (now without it's rim).
2. If the decorative cap is not glued on the stack. After the decorative cap is removed, the rim must be cut off to fit the "Beartrap" casting on the stack. This is done best by a cut circumscribing the stack just under the rim, using the rim as a cutting guide. Looking into the stack will tell you how deep you'll need to cut (about 1/8").
3. The newly cut edge of the stack will be a little rough, both inside and out. I sanded the edges. I also noticed that the cutting caused some of the paint (black with gold flecks) to be chipped. I repainted the entire stack to match the new "beartrap", so both match. If you get no chipping or the chipping is confined to the edge of the stack, painting the stack may not be needed. If you later wanted to use the stack without the "Beartrap" or use the decorative cap (just plugged back in) you may want to paint the stack.
4. Follow the instructions in the Beartrap kit.
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   "Colorado & Southern `Beartrap' Ridgeway Spark Arrester"
   #41550 - $19.95