Work platform:
Werner Aluminum Pro Deck Work Platform, 300 lb capacity, AP-30
For easily reaching a car or truck roof, or working in a truck's engine bay one of these is very helpful. Unlike a 12" wide platform, the 16" width makes the platform much more stable to a side load, which is what you'll get when leaning over to reach something. The leg braces at the ends double as steps so you don't have to make it atop the 20.5" platform in one step. They're also helpful for other jobs, such as painting. I routinely use one for construction work.
There are other, similar models available at home stores, so I'd suggest giving them a try before picking one. I find the Werner products to be strong and stable, but you may find another platform works better for you. Try a 12" wide one and I think you'll agree that the savings over a 16" model isn't worth the lack of stability.