Our Holder can hold Squares of many thickness.
It was designed with Swanson™, Empire and Johnson speed squares in mind.
Some speed squares from china are very thin so the holder works with them without adjustment, others that are made of plastic are very thick and so the slot in the holder will be tight and you may need to shave the plastic slot just a bit to allow the speed square to drop in to the speed square holder easily.
To do this you can use sandpaper or a knife blade dragged along the edge a couple of times on each side will do the trick. The holder will still grip the speed square via the cam system and not drop it out until you pull up on the square.
Here is a video of how to do this
Below are some helpful links on how to use a speed square.