Steel Beams

Steel Beams are a currency unlocked at 40 Stars together with the Tree Upgrades. They are used to get many of the Upgrades in there and also in the future for the Scrapyard v3.

How to get Steel Beams
First, you have to buy an upgrade in the Tree Upgrades to the left with the shape of a Steel Beam (to the right the image of it, to the left the section where you unlock them), and then Steel Beams will fall down every 60 seconds. Swipe it to collect it. At first you'll get one, but you can get up to 12 Beams with several upgrades later on. Note at x130+ Stars: they come at the same time with Tires when they appear.

For Tree Upgrades
Many Tree Upgrades need Steel Beams to be unlocked, one reason why Steel Beams are important to progress faster

For Scrapyard v3
When you get to x75 Stars, you will have the option in the Tree Upgrades to buy the Scrapyard v3, which you feed Steel Beams in to get a Magnet permanent bonus of 1% per level. This scrapyard is simply awesome.