For a long time, we used an awl to scratch the leather to glue the soles underneath the moccasins. 

Then we heard from a ballerina dancer that she used a metal brush to roughen up her dancing shoes so they would stick better. 

That's how we found this metal brush, which makes the preparation for gluing the soles much easier and better. 

So, if you want to glue your rubber or leather soles as a professional, this metal brush is a must-have tool. 

You can see in the third photo the difference between the scratches from the awl in the front and the ones from the Brush at the back and the upper middle. The one in the lower middle part was made with sandpaper, which we do not recommend. See how even the part scratched with the metal brush is.