No tripod? No problem!
Every photographer will eventually face a situation where tripods are not allowed or feasible. I remember a couple years ago going on a trip to Peele Island with the camera club for the weekend and more than 2 hours into driving I realized that the tripod was left behind at home. And I was planing to take some good sunrises shots by the water.
Once I arrived at location, the first order of the day was to find a substitute for a tripod. A large plastic box (the kind you store winter clothes) was the perfect fit. I added a towel to stabilize the camera. And that was my “tripod” for the entire weekend. I managed to take some long exposures using this arrangement.
Another situation I experience recently was the restriction of tripod use. I went to the Hancock Building in Chicago at night and I wanted to photograph the city at night. So at least a few seconds of exposure and bracketing was necessary to capture the image. The solution was to rest the camera on the top of the air vents by the floor. I was very happy with the results.
As long as the camera is stable and not at risk of falling on the ground, other alternatives to a tripod could be used.