Construction happens in the world, not in an editor. Equip a hammer, aim at open ground, and a ghost shows what a click will raise. The ghost is also the refusal: when it runs red, the spot is out of reach, the span too long, the ground too steep, or a body is standing in the line.
Fences
The first thing the hammer builds. Place a post and the pen is down: each click extends a run toward where you aim, intermediate posts filling in at even spacing, and the work costs seconds per post. Aim back at your first post and the ghost snaps shut — click to weld the fence into a closed loop.
Any built fence can be continued from its endpoints — yours or another player's. Pulling works with the other button: pull an endpoint to shorten a fence, a middle post to split it in two, a loop post to open the ring. Pulling costs the same work as placing; nothing heals across a gap on its own.
Fences come in styles — picket, post-and-rail and more — chosen before the first post goes in, and a continued fence keeps the style it was started with. A style changes what you see, never what stops you: the collision is the same solid line whatever the look.