You can vertically stack the units and they somewhat engage but surely not lock. (Most recent Sony Gear has th multi hot shoe) No heat at bottom of feet. The size was also way too small. Thanks, we do order many items from you people the service & shipping is great, but as far as the instructions and geniune stated regarding description is not adequate. The bottom piece that holds the thong over your toes was completely gone. Im sure some of the more expensive options will give you a better sound, or a better muffler, but these are as good as the ones Ive bought, and so far theyre comfortable. I have never had any problems with Skechers tennis shoes so I thought maybe these would be comfortable but they just werent. Comfortable and good looking. Außerdem schützt eine ganz leichte Verdrehbarkeit auch vor Beschädigung, wie ich beim meinem Sturz feststellen durfte, denn da hat sich das ganze einfach weggedreht statt abzubrechen.