This is a basic bracket for a common pneumatic solenoid made by Festo that is used in FIRST Robotics builds and other machines. The bracket allows the solenoid to be easily and quickly removed for tweaking and maintenance without tools. The brackets also make great place holders during a build so the real solenoids don't get beat up while you are running lines and wires. It also makes it easier to share solenoids among several robots since they are pretty pricey.
Updated to V4: I reduced the size of the side tabs to clear another 1mm of space around the wire plugs so the release tab is easier to get to. I also increased the clearance in the wire guides so thicker wires can be stowed behind the towers. That is meant to eliminate strain from he plug itself in the event the wires are staged or otherwise pulled. If you run the wire through the guide before plugging in the connector it will all sure up nicely.
Custom Printer running SMoothieware
I printed this model with Hatchbox PETG at 250C. It's designed to be a tight fit that relies on the PETG to give a bit during instal and removal of the solenoid. There is some minor play once the valve is seated in the bracket but it is very secure. I set the bottom of the bracket to print at .3mm and then switched to .15 for the towers to increase their strength. For setup in Slic3r, that means 0-4.8mm set at .03 and 5.0-22.1 at .15mm in the layer height table. Slic3r also allowed me to print the bracket body with 2 shells but filled in the towers so they printed solid. My final print looks a little sloppy because I don't have the settings for the PETG dialed in just right but I was more focused on fit and function over finish on this piece so I didn't spend time tuning it for anything but strength.
I suspect it could be just as good if printed in TPU with enough shells/walls but it probably won't work well with normal PLA since the side tabs won't won't be able to flex enough to fit the part in without breaking.