Bertlemann slide, or bert, is a skateboarding trick where the skateboarder slides on the wheels of his skateboard. A bert is usually performed on banks or transitions.
When performing a bert the skateboarder crouches down while doing a frontside carve, plants his front hand on the ground and extends his back foot and torso making the back wheels slide out. After the slide the skateboard has made a 180 degree sweeping turn and the skateboarder pushes himself up and continues back to the direction where he came from. When performed in a transition it is possible to convert a bertlemann slide into a grind by timing the slide so that during the apex of the sweep the back truck hits the coping.
A bertlemann was originally a simple turn planted hand that did not involve sliding. It was named after Larry Bertlemann, a surfer who first performed the trick on a surfboard, by the Z-Boys, who imitated Bertlemann's style on skateboards and ended up creating this trick.