Here are two images I hope will make things a bit clearer for those starting out or having filament sticking issues. The first images is typical cross sections at different setups points or levels users find themselves at when trying to set up the proper nozzle height. Each has some information but here is additional as well 1: This is during intial setup when you are trying to ge the x axis to be level by adjusting the two threaded rods some users feel when this is complete printer is ready to go. This is incorrect. You simply have made the z axis across the bed platform but the height is not yet set. 2: This is when you have initially set the z access height by adjusting the screw downward until you first here the click indicating it had been activated There is a significant GRAY area here as the lever action can induce some variablity. 3: This is after new users first try to set up the printer and they think it is OK prints will usually stick but fail shortly after starting mainly because the filament is simply resting on the bed. THIS IS WHERE MOST PEOPLE THINK IT IS A BED SURFACE ISSUE AND TRY THINGS LIKE TAPE AND OTHER TEMPORARY SURFACE ENHANCEMENTS REPEATEDLY WITH CONTINUED FAILURES 4: This is the optimum setting where the filament is lightly flattened this occurs because the filament is actually being pushed down onto the bed surface spreading it slightly. It has a much larger degree of surface contact so successful prints are much more likely disregarding print settings of course. Easily seen if using two loop skirts the filament is spread out just enough so that two loops actually look like a single line as seen in the second pictures This picture shows a nice solid level flattened filament line. The single raised line in the print itself was me lifitng the z axis by hand to see what would happen. This yields good informations as well as it is very likely similar to what is seen in the 2nd or 3rd image just below and while the first layer if made of entirely of these lines may have looked good it most likely would have failed for the reason shown here. 5: Wagon wheel this is when the nozzle is just a tiny bit too low since there is not enough room to really allow the filament to go directly down to the bed the excess squishes out the sides and only leaves a very thin central area this print can recover as subsequent layers do fill in low areas it is best to make the adjustment to get it correct. 6: Skipping or nothing nozzle is extremely low and could cause clogs as the nozzle is trying to extrude some filament does exists at the point and will collect residue from the bed that could cause cloggs so this should be avoided . I hope this helps a lot of people in getting their printers going with the correct initial z height below is an actual image from one of my prints showing some of the characteristics of a good first layer with skirt.