Its still winter up here and a little adjustable portable heater is still useful in my unheated shops. Here is a little project I did many years ago, when my Father passed, I got to clean out his shop materials, one was an old car interior warmer, it no longer had a mounting frame but worked fine. I decided to make up a frame for general use around the house and shops.
Up here, this has become very useful. The angle of heat is adjustable through 90*, pointing to the floor to almost directly upwards. The rubber feet are widely stanced for stability at any angle and the frame is made from one piece of light channel, marked out, cut, drilled and bent to shape.
Its not a tool but through the cold winter months it is one of the most used items in the unheated shops. On a really cold day I can set it up under my tractor blower for a couple of hours for an easy start, comes in handy to keep my feet and legs warm when doing blower repairs or on the bench to keep my hands warm when doing a bench job.