The icons for mounting barbed wire to gates are reversed.

When you try to mount barbed wire to the top of a gate (via the gate attachments icon), it mounts the barbed wire to the bottom of the gate. Vice versa for mounting barbed wire to the bottom of the gate.

1. Build a gate

2. Mount some barbed wire to the top of the gate (using the top gate wire attachment icon as a placement guide)

3. The barbed wire is mounted to the bottom of the gate

4. Alternatively, mount some barbed wire to the bottom of the gate (using the bottom gate wire attachment icon as a placement guide)

5. The barbed wire is mounted to the top of the gate

6. See attached images for refeference

Attaching barbed wire to the top of gate attachment icon, should mount barbed wire to the top of the gate (not the bottom). Vice versa for the reverse.