How do I temporarily unweld mesh compontents?

Okay so basically what i want to do is make a real-time running thing for my character pawn. i have a mesh for each foot, and i want to switch between the mesh being “welded” and following the player’s movement, and staying still. i have the code for the switching part. ive found that setting physics on will make the mesh get left behind, but i can’t figure out how to make it stay with the player’s movement again.