What’s the point of holding a tape measure?

There are two different interpretations of the tape measure.

One explanation is that the joke came from a joke about Ross. In this joke, Ross tells Rachel that he wants to go to "the archives," and Rachel asks him how long it will take to get there, to which Ross replies "Depends on my tape measure." The crux of the joke lies in Rose's response. He didn't say how long it would take him to get there, but how long his measuring tape was. It's a language game that exploits the double meaning of "depends" in English.

Another explanation is that holding a tape measure means that the two of them have no chance of having an in-depth relationship. During a blind date, if the other party mentions or leaves a tape measure, it means that the other party wants to keep a distance from each other, that is, the two of them do not have to have an in-depth relationship.