I installed service rails on my Met Pro last night. I picked them up from PBL. The instructions were really good, even telling you what size drill bit to use etc. I used by TFLE that has service rails from factory as a comparison for where to drill. The Met Pro playfield doesn't have any marks to indicate where they would go. Anyways. It took just about 45 minutes. I worked very slow and careful. It was kinda unnerving to drill holes through/into the playfield! But the end result is fantastic! Now you can reach all the way to the back of the sparky chair etc without having to be a contortionist!

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After drilling hole through the left side
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After drilling hole through the right side
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Next step was to hammer in the provided T-nuts into the holes you just drilled.
Then lift the playfield to full up position and loosely attach the rails using the provided machine screws.
This will allow you to pick a spot on the under side of the playfield to mount the bottom part of the leg.
Again there are no premarked dimples or anything to show you where to go on this. I just did what seemed to make the most sense for me. Checking clearance with under playfield wires and mechanical stuff.

I used a pencil and marked the holes where I wanted to mount the lower legs to the playfield

Left
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Right
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This is a very important tip. I wrapped several layers of tape on the drill bit with just a little bit of the bit showing. this will prevent you from running the bit clear through to the top of the playfield.

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Then VERY CAREFULLY drill on each of the four pencil marks you have made.

The last step is just to screw in the provided screws into the holes you just drilled and secure the legs to the playfield. Then I went back and tightened the top machine screws (into the T-nuts you installed earlier).

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Done!