Smilies are a common problem with all new builders. They occur when the rivet gun is not held at 90° angle and firmly against the rivet head.
The result is possible damage on the rivet head and / or smilies (dents) in the rivetted material. Needless to say this has to be avoided as much as possible.
A very good trick is to tape some duct-tape or mylar tape on the universal rivet set head. It worked great for me.
The correct procedure to rivet is to set hold the rivetting set on the head, run the trigger and when finished, don't move the rivet gun away from the rivet until the fun is completely done moving.
A common mistake is that people set a perfect rivet but then tilt or move the rivet set when they released the trigger and the set is still moving.
This causes denting on the material and evantually a damaged rivet head.
Always keep the rivet set steady and pressed against the rivet until the gun comes to a complete stop.
