Elbow-knee connection is one of the most important tools in the guard retention toolbox, and if you want your opponent to have a tough time passing your guard then you have to develop this skill. This concept and many others are covered in much greater detail in The Guard Retention Formula that I put together with BJJ black belt Rory Van Vliet – more info here: https://www.grapplearts.com/guardretention

In order to pass your guard your opponent needs to invade the space between your knee and your elbow, so use elbow-knee connection to deny him that space. From https://www.grapplearts.com/oldguard, the instructional for grapplers 40 and over, available in DVD, online streaming, and app-based formats featuring Rob Biernacki and Stephan Kesting

From https://www.grapplearts.com/guardretention. The twist sweep is a fantastic defense against pressure passing in general, and the over-under pass in particular!