A total of 17,000 troops have been posted along the frontier to prevent Venezuelan gas and other products kept cheap thanks to government price controls from being sneaked across the border into Colombia.
The closing along 2,200 kilometers (1,400 miles) of border applies only at night. It will last 30 days during a preliminary period and then the effect of the measure will be assessed.
The lure for smugglers is acute: gas is so cheap in Venezuela it costs less to fill up your tank than it does to buy a bottle of water.
Even Venezuelan President Nicolas Maduro admitted a few months ago that selling a liter of milk at the border brings in more money than selling cocaine.