You can find thresholds at home centers and lumberyards. If you are cutting stock for a custom threshold, use a table saw to cut a dado in the edge facing the highest surface.
A threshold provides a visual and mechanical transition between one type of floor and another. The threshold shown is curved; you can also purchase a flatter version.
When the carpet meets a raised floor, such as a thick tile floor, use a threshold that screws down through the carpet and angles to provide a smooth transition.
Like the height change threshold, this threshold connects flooring materials of two different heights.
This transition joins carpet to an existing floor. Nail the edging to the floor and stretch the carpet over the barbs. For a snug fit, tap down the curved edge.
An alternative option is to butt the carpet against the hard surface flooring and place a marble threshold over the edge. A special adhesive attaches the marble.
Like the marble threshold, the faux-stone threshold provides another option for butting carpet against hard-surface flooring.
This wood molding covers the carpet and butts against a wood floor. Nail the piece to the subfloor.
from looking at the options, I guess an adhesive with marble or stone.
what kind of indoor threshold do I use between tile and concrete dyed floors
Three simple projects to cross off of your to-do list -- just print these instructions and begin!