I posted this idea some time back - not sure if I was first though. I use this also as insurance whan I ship handguards also. I came up with the idea while repairing a cracked handguard. After you put the epoxy in the crack, snap the coins in and the epoxy will mostly sqeeze out. Wipe with vinegar and the crack will usually be as invisible as can be and, just as importantly, you will not be inducing new stresses caused by creating an epoxy wedge in the crack.