Everybody’s pretty familiar with standard wood or rubber wedges; primarily to hold doors open, but in the fire service we use them for that and more – forcible entry, to help stem the flow of fire sprinklers, and yes, to hold doors open.
This is a standard-issue spring clamp – as you can see here, it can be applied to most doors without any issue (although you’d do well to keep the rubber tips on to keep from scratching them).
Also, it clips handily to a large keyring, a radio strap, or a bunker coat as pictured above. I’m a big fan of the spring clamp for general use, especially for keeping doors that have been forced open or opened with a key in the open position, while allowing the door to be mostly closed, helping to avoid attracting undue attention.
The other wedge we have at my work is called the Fat Ivan – it’s a foldable door chock that comes with magnets built in for easy storage.
To use it, you just open it up wide and slide the metal hook over the hinge; one interesting feature is that it holds the door open at approximately a 90 degree angle – useful if you have to move things through the door, not so useful if you want to avoid attracting a bunch of attention (or hot/cold air) with the open door.
Here it is installed – you can just barely see the hook peeking over the hinge in the right hand photo.
To store it, you can put the hook through a keyring or another loop and then close the Fat Ivan and it’ll stay in place until you need it; the only disadvantage I find to this method is I often forget it’s there!
Hope this helps guide your selection, and I’ll say that if you need something that can just slip into a pocket, a small wooden wedge is about perfect – some things are classic for a reason.
-T