Quick Connectors are our preferred method of fastening extrusion and is the Framing Tech standard when designing frames.  They offer a superior connection vs Connection Screws and are very easy to use.  For 30mm series extrusion, an 11mm hole is drilled into the extrusion to receive the barrel.  For 45mm series extrusion, a 17mm hole is drilled into the extrusion to receive the barrel.  The hammer is then inserted into the centerbore of the extrusion and into the barrel.  A set screw is then inserted and tightened slightly to align the hammer.  After inserting the exposed head of the hammer into an adjacent piece of extrusion, simply tighten the set screw fully.  This pulls the head of the hammer back, creating a strong connection with the adjacent extrusion.