This is a cable protector, designed to protect a single extension cable from damage by someone walking on it.

This object is expected to be used with a mat or rug over top, to prevent users from kicking it up off the floor. 
 This does NOT (yet) have pins or restraints designed to keep it from being knocked around.

The interior groove is 11mm wide and ~10mm tall, which was, in my testing, large enough to cover a "standard" USA extension cable.

I tested it for a few minutes, including briefly stamping directly on it on a concrete floor, and it appeared to hold up, at least for now. All of my load testing was unoffical.
 
My print settings:

Inland PLA+
205 degrees C hotend
60 degrees C bed
4-wall perimeters on all sides
15% infill, GRID pattern 
No supports required if printed flat (like it would be on the floor)

dimensions:
210 mm (8.27 inches) long 
90 mm (3.54 inches) wide 
14 mm (0.55 inches) high 
(You might be able to make it 1 mm shorter if you're feeling adventurous, but I wouldn't go much below that)

Print time was about 2h 10m on my printer but your print times may vary.

Heavily inspired by https://www.printables.com/model/235442-cable-cover-for-floor-with-screwholes 
My modification changes the center groove to be a 45 degree angle chamfer rather than a rounded hole to allow for printing flat without requiring supports. For me, I found this improved printing speeds as well, as most of the motion is now on the X axis rather than on the Z axis.
 
I have provided the OpenSCAD file for anyone who wants to tweak or play with the design. 
I left a lot of comments in the OpenSCAD code, so hopefully even someone new to OpenSCAD can play with a few variables and see what they do to affect the shape.