From dKosopedia

A roadblock set up to check people for arms, immigration status, etc.

Used extensively by Israel inside the Palestinian Territories, and not merely on the border between Israel and the West Bank and Gaza Strip. These barriers ("machsom" in Hebrew) were first erected after the signing of the Oslo Accords, predating the recent waves of suicide bombing. Their stated aim is to prevent such acts of terrorism but they also have the effect of preventing free movement through the area, with all the attendant problems for journalists, medical personnnel, anyone wishing to visit family or any other travel through the Palestinian territories. They do not affect Israeli settlers who by and large use a system of bypass roads to get around.