Klinko's is a copy and office supply store that Stelio Kontos works at.
When Stan tries to toughen up Steve in "Bully for Steve", he recounts his beatings at the hand of Stelio which stopped when Stelio moved away. When Steve gets tired of being pushed around by Stan, Steve locates Stelio at the Klinko's copy store through Facebook and hires him to beat up Stan until he surrenders and agrees to quit picking on Steve.
When a bully named Luis Ramirez picks on Steve Smith in "The Full Cognitive Redaction of Avery Bullock by the Coward Stan Smith". Steve goes to Roger for help and he brings in Stelio to beat Steve up first, explaining that the bully will reject Stelio's sloppy seconds. As Steve laments having trusted Roger, Luis actually rejects him and Steve sends him to find Stelio to beat him up instead. As he confronts Stelio at Klinko's, he fawns all over him as a legend and talks Stelio into joining together to beat up Steve.