Similarly to the ammo crates, in most standard games each player gets to deploy one tank trap anywhere this is no other terrain feature.
In game terms; tank traps prevent a vehicle from entering a square and provide hard cover for infantry.
These are the plastic ones you get with the Dust Tactics: Revised Core Set.
Nothing complicated here, grey spray undercoat with a white spray dusting, gentle wash on the base and them a dry-brush before matt varnish.
You get a few more with some of the other scenario sets although there are very few scenarios in Dust Tactics when you actually need many more than two.