The Two Ways to Join Objects in Roblox Studio

You can connect two objects in Roblox Studio using either welds or anchoring with proximity. A weld is a permanent joint that locks two parts together so they move as one unit — this is what you use when you want a handle attached to a door, or wheels attached to a car. Anchoring is simpler but less flexible: you lock each part in place individually, which works for static scenery but not for moving assemblies.

The weld method is more common in games because it lets you build complex moving objects. When you weld Part A to Part B, Part A follows Part B everywhere — if Part B rotates, Part A rotates with it. If you delete Part B, Part A disappears too. This dependency matters when you're building something that needs to stay together.

This guide covers welding, which is the technique you'll use most often. Anchoring is mentioned only because beginners sometimes confuse the two.

Key Takeaways

  • A weld connects two parts so they move together as a single object, with one part as the parent and one as the child.
  • You create a weld by inserting a WeldConstraint object into one of the parts, then setting its Part0 and Part1 properties to the two parts you want to join.
  • The part you set as Part0 is the parent — if you delete it, the child part disappears too, so choose carefully.
  • You can test whether a weld is working by moving one part in the viewport and watching whether the other follows.

Setting Up Your Two Parts Before Welding

Before you weld, position both parts roughly where you want them to be. Open your workspace in the Explorer panel on the left side of Studio. You should see both parts listed there — for example, "Handle" and "Door". Click on each part in the viewport to select it, then use the Move tool (press M) to position them close together.

The parts do not have to be touching perfectly — the weld will hold them at whatever distance and angle they are when you create it. If you want a handle to stick out from a door by exactly 2 studs, position it that way before welding. Once the weld is in place, you cannot adjust the distance without deleting the weld and starting over.

Write down which part should be the parent (the one that controls the motion). Usually this is the larger or more important part — the door rather than the handle, the car body rather than the wheel. The parent part is the one you will move or rotate in your game, and the child will follow automatically.

Creating a WeldConstraint and Connecting the Parts

Right-click on the part you chose as the parent in the Explorer panel. Select Insert Object. A menu will appear with many object types. Scroll down and click WeldConstraint. A new WeldConstraint object will appear in the Explorer, nested inside your parent part.

Click on the WeldConstraint in the Explorer to select it. In the Properties panel on the right side of Studio, find the property called Part0. Click in the empty box next to Part0. The cursor will change to a crosshair. Now click on the parent part in the viewport — the same part that contains the WeldConstraint. The property box will now show the name of that part.

Next, find the property called Part1 in the Properties panel. Click in the empty box next to Part1. The cursor will change to a crosshair again. This time, click on the child part in the viewport — the part you want to attach. The property box will now show the name of that part. The weld is now active.

Testing Whether Your Weld Is Working

Click on the parent part in the viewport to select it. Press M to set up the Move tool. Drag the part around the workspace. Watch the child part — it should follow the parent smoothly without separating. If the child part stays in place while the parent moves, the weld did not connect properly. Go back and check that both Part0 and Part1 are set to the correct parts.

Try rotating the parent part as well. Press R to set up the Rotate tool. Drag one of the rotation handles. The child part should rotate with the parent, maintaining the same angle and distance. If it does not, delete the WeldConstraint and try again, making sure you clicked on the correct parts when setting Part0 and Part1.

Once the weld is working, click the Play button at the top of Studio to test it in the game. The weld should hold during gameplay. If the parts separate when the game runs, the weld is set up correctly but something else in your game code is moving one part independently — check any scripts that touch either part.

Fixing Common Weld Problems

If your parts are separating even though the weld looks correct, check whether either part is anchored. An anchored part ignores welds and stays frozen in place. Select each part, look at the Properties panel, and find the Anchored checkbox. If it is checked, uncheck it. The child part should never be anchored. The parent part can be anchored if you want it to stay still, but usually you leave both unanchored so the weld can move them together.

If the weld is set up but the parts are not where you want them, you cannot adjust the distance by moving one part — the weld will snap it back. Instead, delete the WeldConstraint, reposition both parts, and create a new weld. Right-click the WeldConstraint in the Explorer and select Delete.

If you have more than two parts to connect — for example, a wheel, an axle, and a car body — create separate welds for each pair. Weld the wheel to the axle, then weld the axle to the car body. The motion flows down the chain: if you move the car body, the axle moves with it, and the wheel moves with the axle.

When to Use Anchoring Instead of Welding

Anchoring is simpler than welding but it does not create a joint. When you anchor a part, it straightforward locks in place and will not move unless a script moves it. Use anchoring for scenery that should never move — buildings, trees, terrain props. Select the part, find the Anchored checkbox in the Properties panel, and check it.

Do not use anchoring to connect moving parts. If you anchor both a wheel and a car body, they will not move together — they will stay frozen in their current positions. Anchoring is a lock, not a joint. Welding is the tool for assemblies that need to move as one unit.

Frequently Asked Questions

What happens if I delete the parent part?

The child part disappears too. The weld creates a dependency: if the parent is gone, the child has nothing to attach to. This is why you choose the parent carefully — usually the part that should survive if something goes wrong.

Can I weld more than two parts together?

Yes, but you create multiple welds, not one weld that connects three parts. Weld Part A to Part B, then weld Part B to Part C. Part B becomes the middle link. Motion flows through the chain.

Can I change which part is the parent after I create the weld?

Not directly. You would need to delete the weld and create a new one with the parts reversed. Select the WeldConstraint, right-click it, and choose Delete. Then insert a new WeldConstraint into the part you want as the new parent.

Why do my welded parts separate when I run the game?

Check whether either part is anchored — anchored parts ignore welds. Also check whether any script in your game is moving one part independently. If a script uses MoveTo or sets the Position property on the child part, it will override the weld.

Do I need to weld parts that are just sitting on top of each other?

No. If gravity is holding them together and they do not need to rotate or move as one unit, you can leave them separate. Welds are for assemblies that must move together or rotate together.