ItemKitLinearRail (multi-constructor kit for rail pieces)

Overview

ItemKitLinearRail is a MultiConstructor item: a single held stackable kit that offers multiple structure build options through the radial selector. Its eight constructables are the eight "linear rail" track pieces for the Larre robotic-arm rail system.

Prefab name: ItemKitLinearRail (confirmed via resources.assets GameObject name scan).

Prefab path_ids observed: 38053 and 41664 (one is the in-world item; the other is the mirrored / cursor preview variant).

MultiConstructor base class

Assets.Scripts.Objects.MultiConstructor is the base kit type. All "multi-build" held kits in Stationeers use this class:

namespace Assets.Scripts.Objects;

public class MultiConstructor : Stackable, IConstructionKit, IConstructionStarter, IReferencable, IEvaluable
{
    [Header("Multi-Constructable")]
    public List<Structure> Constructables = new List<Structure>();

    [NonSerialized]
    public int LastSelectedIndex;

    public override void OnPrefabLoad()
    {
        base.OnPrefabLoad();
        for (int num = Constructables.Count - 1; num >= 0; num--)
            if (Constructables[num] == null)
                Constructables.RemoveAt(num);
        if (LastSelectedIndex >= Constructables.Count)
            LastSelectedIndex = Constructables.Count - 1;
    }

    public virtual void Construct(Grid3 localPosition, Quaternion targetRotation, int optionIndex,
        Item offhandItem, bool authoringMode, ulong steamId)
    {
        int entryQuantity = Constructables[optionIndex].BuildStates[0].Tool.EntryQuantity;
        Construct(localPosition, targetRotation, optionIndex, offhandItem, authoringMode, steamId, entryQuantity);
    }

    public virtual void Construct(Grid3 localPosition, Quaternion targetRotation, int optionIndex,
        Item offhandItem, bool authoringMode, ulong steamId, int quantity)
    {
        if (authoringMode || OnUseItem(quantity, null))
        {
            CreateStructureInstance createStructureInstance = new CreateStructureInstance(
                Constructables[optionIndex], localPosition, targetRotation, steamId);
            if (PaintableMaterial != null && CustomColor.Normal != null)
                createStructureInstance.CustomColor = CustomColor.Index;
            if (GameManager.RunSimulation)
                Constructor.SpawnConstruct(createStructureInstance);
        }
    }

    public List<Thing> GetConstructedPrefabs()
    {
        List<Thing> list = new List<Thing>(Constructables.Count);
        foreach (Structure constructable in Constructables)
            list.Add(constructable);
        return list;
    }
}

Key points:

• Constructables is a List<Structure> populated via Unity's SerializeField in the prefab (Inspector-assigned). It does NOT live in decompiled source; a prefab extraction is the only way to read it.
• MultiConstructor inherits from Stackable, not from Item directly. The kit is stackable in inventory.
• The kit's own CustomColor propagates to the spawned structure via CreateStructureInstance.CustomColor: if the player has painted the kit itself, every placed rail spawns pre-painted that colour.
• MultiConstructor is the same base class used by every kit with a radial option selector (e.g. pipe kits, wall kits, chute kits). It is not rail-specific.

Constructables list (the 8 rail prefabs)

The Constructables list is populated in the prefab, not in code. Direct typetree extraction via UnityPy failed silently on the MonoBehaviour attached to the ItemKitLinearRail GameObject (path_id 104509 referenced the rail's MonoBehaviour; the typetree read raised Expected to read 64432 bytes, but only read 32 bytes, which is a UnityPy compatibility issue with this particular serialized field layout).

The eight rail-only prefabs confirmed in resources.assets under the StructureRoboticArm naming convention are the only candidates that match "linear rail" semantics (dock / junction / bypass variants each have their own ItemKit prefabs — ItemKitLarreDockAtmos, ItemKitLarreDockBypass, ItemKitLarreDockCargo, ItemKitLarreDockCollector, ItemKitLarreDockHydroponics):

1. StructureRoboticArmRailStraight
2. StructureRoboticArmRailStraightStop
3. StructureRoboticArmRailCorner
4. StructureRoboticArmRailCornerStop
5. StructureRoboticArmRailInnerCorner
6. StructureRoboticArmRailOuterCorner
7. StructureRoboticArmRailScrewLeft
8. StructureRoboticArmRailScrewRight

Eight entries match the user's stated "8 rail part classes." The order is prefab-inspector-defined and was not extracted; consumers should iterate Constructables rather than assume a specific index.

Every one of these prefabs binds to either Objects.RoboticArm.RoboticArmRailStraight or Objects.RoboticArm.RoboticArmRailInnerCorner at the C# level; see RoboticArmRail.md for the full class roster and connection model.

Note the older StructureRobotArmRail* (no "ic") prefabs also exist in resources.assets: StructureRobotArmRailControlBox, StructureRobotArmRailCorkscrewL, StructureRobotArmRailCorkscrewR, StructureRobotArmRailCorner, StructureRobotArmRailCornerInner, StructureRobotArmRailCornerStop, StructureRobotArmRailCornerVertical, StructureRobotArmRailStraight, StructureRobotArmRailStraightStop. These are a legacy generation retained in the asset bundle and are not the current ItemKitLinearRail constructables. Mods that want to cover both generations need to handle both prefab-name prefixes.

Construct flow

Player selects a rail piece via the radial on the kit; LastSelectedIndex persists the last pick on the kit instance. On placement, MultiConstructor.Construct(..., optionIndex, ...) consumes Constructables[optionIndex].BuildStates[0].Tool.EntryQuantity from the stack and spawns the structure through Constructor.SpawnConstruct(createStructureInstance). The spawn runs server-authoritative (GameManager.RunSimulation).

Verification history

• 2026-04-20: page creation. MultiConstructor source cited verbatim from decompile; ItemKitLinearRail prefab existence verified via resources.assets GameObject name scan; 8-entry rail-prefab list inferred from the prefab naming pattern and the absence of any other rail-only kit in the prefab list.

Open questions

• Exact Constructables list order and presence of any non-obvious entry (vertical-corner / stop / corkscrew variants that could be hidden). Resolving this requires either a successful typetree extraction of the MonoBehaviour, a Mono.Cecil inspection of the MultiConstructor-derived asset block, or in-game observation of the radial menu.