you all familiar with a very common one way barrier with have spikes on spring. It let’s you pass only one way, otherwise will punch your wheels.
For example: http://img2.wikia.nocookie.net/__cb20120401082221/drivingworld-htif/images/4/4f/Road_spikes.jpg
How would you map it? barrier=spikes ?
The Barries wiki page gives this image for barries=spikes as example:
Which is clearly not my case.