Razor Wire is a transparent, semi-tangible block added by Immersive Engineering. When an entity, including the player, walks through or touches the block, they will be slowed for the duration of contact with the wire, as well as taking damage each half-second. The amount of damage received depends on if the entity is wearing leggings or boots. If the entity is not wearing leggings or boots the damage will be 1.5, if wearing one of those armor pieces the damage will be 1, and if wearing both the damage will be 0.5.
Razor Wire can be electrified by connecting it to an LV Wire Coil, which will increase the damage by 2. This does consume any energy.