This is a solid thru solid penetration trick.  Two solid bars are displayed, and the trick can be done in a way where you hand them out for examination after the trick. (Print an extra) I also added the key chain, but you can use a string or rubber band, the chain makes the “Secret Part” work easier.   Not much other explanation needed, here is a link to a video demonstration.    The chain I use is called “ball chain” or “link chain” on Amazon