This is consumable splinter guard for Festool TS 55 R track saw (Festool SP-TS 55 R).
2017-05-29 update: Part updated after real life cut testing. Only one thing changed - flat tab in front was too long and prevented sliding guard below the top surface of the track. Download updated stl and replace the old one, please.
Measure precisely and adjust filament diameter in slicer to achieve correct dimensions and good fit.
Supports needed under horizontal surfaces only - adjust slicer settings accordingly. See the last picture.