I tried couple of different key holders with fabrics. I got some magnetic buttons and key rings from shops.

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Inside of Cat Key holder..

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Mouse shaped key holder...
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House shaped key holders

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If you pull the handle, keys will get inside and not to be seen. No jingling sound either...
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You might have already guessed how I made them, but if you'd like to see some detail, these photos on how I made a very similar name tag accessory to attach to school bag can shed some lights. This is a name tag for a car loving boy.

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First, I drew a pattern just the way I want...
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Cut the fabrics according to the patterns
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Appliqued them..
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Wheels are made separately..
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When the appliqued-top is finished, place right side of this top on the right side of lining fabric. At the bottom put battings. Sew along the line leaving some space as an opening window. Tidy up the seams, then turn it over through the window. Many tiny snips can be useful.
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Close the window with blind stitches and do decorating stitches including the name for the owner.
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Connect the sides of front and back with blind stitches.
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Attach a rubber string. If you tie a key ring at one end, you can use it a  key holder.
 
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