Abstract: A connecting plug for providing lateral support for a circuit board in a plug-in unit intended to receive electrical and electronic components in industrial electronic devices, wherein the plug-in unit includes a front panel and circuit board fastened to the rear of the front panel and perpendicularly thereto by means of at least two holding blocks. The connecting plug includes a body provided on one side with at least one insertion groove for receiving a circuit board. A plug-in pin projects from the opposite side of the body and is shaped to provide a press seat with a blind recess provided in a rear face of a front panel of a plug-in unit to prevent the connecting plug from dropping off such front panel.