The trim is clay made, usually softer than a ceramic made one.
eBay
10Pcs Heavy Duty 90° Iron L Corner Brace, Thickened Steel Right Angle Bracket for Furniture Shelf
Aliexpress UK
Corners, top and edge trims, all at 2.7m length and available in a choice of finishes.
eBay
110V-220V Mini Pen Sander Model Polishing Grinding Gundam Military Model Grinding Round Corner Polisher Grinder Tool Machine
Aliexpress UK
Hook and Loop 90 Degree Inside Corner Sanding Block Sandpaper Grinding Holder Drywall Wood Abrasive Hand Sanding Pad 180#
Aliexpress UK
96/8pcs Carpet Non-slip Sticker Reusable Washable Anti Curling Carpet Patch Fixed Stickers Floor Rug Mat Tape Gripper Corner Pad
Aliexpress UK
8Pcs Metal Crafts Decorative Wood Box Feet Leg Corner Protector Guard Bracket For Furniture Antique Bronze Hardware
Aliexpress UK
180 Degree 2pcs Foldable Hinge Flap Screw-On Hinges For Sewing Machine Cabinet Rounded Corner Buffer Hinge Furniture Hardware
Aliexpress UK
Pen Type Mini Sander Stroke Grinder Machine Reciprocating Sander Model Sander Groove Grinding Tools Round Corner Polisher
Aliexpress UK
Anti Slip Rug Tape Carpet Sticker Reusable Self-adhesive Anti Curling Fixed Carpet Patch Mat Tape Gripper Corner Pad Wholesale
Aliexpress UK