I recently bought a new home. When going to change the furnace filter, I couldn't get the original furnace filter out of the slot at the last part of the filter (where the cardboard border is). Since it was a cheap used filter, I wasn't too worried about destroying it, so I just kept yanking while holding the air duct in place, and eventually ripped it out. After removing the old filter, I noticed that the top lip of the furnace filter slot, going into the air duct, was bent downward a little bit. It's not bent a lot, but enough that the cardboard will get caught while removing the filter. It is a major pain.

I tried getting a hammer in the tight (1") opening, but I couldn't seem to do anything with a hammer. I tried bending the metal metal with my hands, but the metal would just go right back to where it was originally. I want to get a nice permanent electrostatic furnace filter, but I am scared that I will put it in there and never be able to get it out to clean it. Cardboard will rip and break, metal will be a little harder to destroy to get it out of the air duct. Does anyone have an idea on how to fix this problem? I really don't want to have someone come out and replace the air duct just for one small bent piece of metal. Below is a picture of the setup.

enter image description here

  • Can you get a pair of pliers in there to bend it back?
    – Steven
    Commented Feb 12, 2013 at 14:15
  • I tried using a set of vice grips a couple days ago, but it didn't really help. I couldn't really position them well enough. If I can remember, I am going to take a picture and upload it so people can see the odd predicament I am in.
    – David
    Commented Feb 13, 2013 at 4:56
  • @David That picture is awfully blurry, and it's hard to see any detail of the slot. I recommend you try again and make sure your camera's autofocus locks in properly. (Also reduce the resolution before uploading, if you can.)
    – Kevin Reid
    Commented Feb 14, 2013 at 2:57
  • Hi @KevinReid, Thank you for your comment. I will try to get another picture tonight and update it. It is dark in my garage. I took around three pictures, and this was the best of the three. I will see if I can get some extra lighting in there.
    – David
    Commented Feb 14, 2013 at 22:05
  • @KevinReid, Sorry for the delay. I had some crazy stuff happen and spaced this. I have updated the picture. It looks MUCH better now.
    – David
    Commented Feb 27, 2013 at 5:15

1 Answer 1


It sounds as if the slot is OK at least on one side of the bend, or perhaps both. If so you can make a shaper out of a piece of wood whose thickness is cut to the width of the slot.

Insert the wood in the good section of the slot and force it through the bent section. You may even be able to tap it sideways with a hammer.

If the wood is too soft to bent the metal back, try a harder piece of wood or even a piece of metal if you can find one of the right size. A piece of wood layered to the right thickness with a thin piece of metal toward the bent side of the track would also work.

  • That is a great idea, but the exhaust stack goes in front of the area where you put the furnace filter in (almost to the point where you can't replace the furnace filter)... I am going to take a picture to show the layout of my furnace.
    – David
    Commented Feb 13, 2013 at 4:59
  • Hi @bib, I have added a nice picture of the scenario. Do you have any ideas for bending the top lip upward after seeing the updated picture? It is difficult to get anything in there to bend the top lip upwards....
    – David
    Commented Feb 27, 2013 at 5:17
  • 1
    @David-It sounds like you are thinking the wood needs to be the width of the filter. No, it may be any useful width, actually the narrower (within reason) the better. (@bib-I was reluctant to speak for you, but in the end decided time was more important) Work segments of metal a small amount at a time, pushing the wood down, levering the lip upwards, just enough that it passes it's elastic limit and does not spring back all the way to it's original position. Doing this several times is better than all at once. Also tap above the wood on the vertical metal with a hammer to enhance the folding.
    – bcworkz
    Commented Feb 27, 2013 at 19:22
  • @bcworkz: Thanks for your comment. I will see if I can make a shim and a hammer do the job. I was thinking a huge piece of wood for some reason. Thanks again!
    – David
    Commented Feb 28, 2013 at 1:23

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