Only thresholds I had was where it changed from carpet to hardwood. They just made sure to stop the movement before the threshold and put the next slider/skid over the threshold where the skid/runner end wasn't on the threshold, it was more toward the center(I hope this is clear). After reading my first post, I noticed I have it all upside down. Literally. The plastic on the skids went up allowing the safe to slide on the runner/skid. The rubber(if that is what it was) went down on the carpet/hardwood and provided enough friction (I guess) to keep the runner from moving. The safe slid on the white plastic not the rubber. Two guys moved the safe, one pushed and all the second guy seemed to be doing was make sure it didn't get pushed over. They slid the safe sideways, with the door pointing in the direction the safe was going.