Vintage Story models historical technology well:

: Once the enclosure is set (typically a 3x3 or 2x3 area of stakes), right-click the center stake on the far side to finalize the trap.

Tip: You will need quite a few of these to make an effective catchment area. It is recommended to craft at least 10 to 20 traps to start.

Think of a Weir Trap as a "lobster pot" for land animals. It is a structure made from sticks and dry grass that allows an animal to wander inside but prevents them from finding their way back out.

You don’t need a crafting table or advanced tools to build a Weir Trap. Here is the breakdown: