Threshold (or door sill) is the strip or profile at the bottom of a door opening that forms the transition between two floor surfaces (e.g. interior and exterior) and seals the gap under the door. Aluminium thresholds are door sills made from extruded or milled aluminium profiles.
✅ Provide structural support under the door
✅ Seal against water, air, dust, and drafts
✅ Provide a smooth transition and reduce tripping hazard
✅ Improve thermal insulation (when designed appropriately)
✅ Withstand foot traffic and wear
Because aluminium is lightweight, corrosion-resistant, and strong, it is a common choice for thresholds, especially for aluminium door systems.