What is the meaning of a "broad rail" in the court? I have tried to find its meaning from a dictionary, but I couldn't find this particular collocation. It is used in the context where the policeman leads an accused person up to the broad rail during the court session, for example. What are the possible synonyms for a "broad rail"?
The rail refers to the bar separating the public area of the courtroom (the gallery) from the area where only court personnel (e.g. the judge, bailiff, court reporter) and people involved in a trial (i.e. plaintiffs, defendants, legal counsel) are allowed to enter. Based on the limited context of "a policeman leading an accused person up to the broad rail during the court session," I would guess that the policeman is escorting him to the bar, where he will then step from the gallery into the "trial area."
Another source I found describes defendants as once standing at the bar during a trial and facing the witness box (i.e. the layout has changed in modern times).
In short, the policeman is taking the accused person to the bar of the courtroom to either enter the "trial area" or to stand at the bar, depending on the time period in which your example takes place. I couldn't find any special meaning for broad in this context; I believe it is being used as a literal description of the rail.