The basic way to connect two objects: using Welds

The most straightforward way to connect two objects in Roblox Studio is to use a Weld, which locks two parts together so they move as one unit. When you weld Part A to Part B, Part A will follow Part B's position and rotation — if Part B moves, Part A moves with it. This is different from just placing parts next to each other, because a weld creates a permanent mechanical bond.

To create a weld, you need two parts already in your workspace. Select the first part you want to connect, then hold Ctrl (or Cmd on Mac) and click the second part to select both. Right-click on one of the selected parts and choose Insert Object, then select Weld from the menu. Roblox Studio will automatically create a weld that connects them at their current positions.

The weld appears as an object in the Explorer panel under one of your parts. You can see its properties in the Properties panel — the important ones are Part0 and Part1, which show which two parts are connected. If you ever need to remove the connection, you can delete the weld object and the parts will no longer be locked together.

Key Takeaways

  • A Weld is the standard tool for connecting two parts so they move together as a single unit in Roblox Studio.
  • To create a weld, select both parts, right-click, choose Insert Object, and then select Weld from the menu.
  • The weld object appears in your Explorer panel and shows which two parts it connects through its Part0 and Part1 properties.
  • Deleting a weld breaks the connection between parts without removing the parts themselves.
  • Welds maintain the exact distance and angle between two parts, so they stay in the same relative position even when moved or rotated.

Understanding Part0 and Part1 in the Weld properties

When you create a weld, Roblox assigns one part as Part0 (the primary part) and the other as Part1 (the secondary part). Part1 will follow Part0's movement — so if you move Part0, Part1 moves with it, but moving Part1 alone won't move Part0. This matters when you're building something like a door on a frame, where you want the door (Part1) to follow the frame (Part0).

You can change which part is Part0 and which is Part1 by clicking on the property in the Properties panel and selecting a different part from the dropdown. Switching them changes the behavior of your connection. If your welded objects aren't moving the way you expect, check which part is assigned as Part0 — that's the part that controls the movement.

Using Motor6D for moving parts that need to rotate

A Motor6D is similar to a weld but designed for parts that need to rotate or move relative to each other, like a character's arm rotating at the shoulder or a robot's leg bending at the knee. Motor6D is what Roblox uses inside character models to connect limbs to the torso. If you're building something that needs joints or moving parts, Motor6D gives you more control than a regular weld.

To create a Motor6D, follow the same steps as a weld: select both parts, right-click, choose Insert Object, and select Motor6D. The Motor6D will appear in your Explorer panel. You can then adjust its C0 and C1 properties to control the angle and position of the connection. The C0 property controls the offset from Part0, and C1 controls the offset from Part1.

Motor6D is more complex than Weld because you're working with coordinate frames instead of simple positions. If you're just connecting two static parts that shouldn't move relative to each other, use Weld. Use Motor6D only when you need parts to rotate or bend at a joint.

Connecting parts with constraints for realistic physics

If you want two parts to stay connected but still respond to physics — like a rope that can stretch or a hinge that can swing — use Constraints instead of welds. Constraints are more flexible than welds because they allow some movement while still keeping parts connected. Common constraint types include BallSocketConstraint (for ball-and-socket joints), HingeConstraint (for hinged doors), and RopeConstraint (for rope-like connections).

To add a constraint, select both parts, right-click, choose Insert Object, and browse to the Constraints folder. Select the type you want. Each constraint has properties you can adjust — for example, a HingeConstraint has an AngularVelocity property that controls how fast it rotates, and a LimitsEnabled property that lets you restrict how far it can swing.

Constraints are useful when you want objects to feel more realistic and interactive. A door connected with a HingeConstraint will swing open and closed naturally. A rope connected with RopeConstraint will sag under gravity. If you want rigid, unchanging connections, stick with Weld. If you want movement that feels physical, use Constraints.

Checking your connections in the 3D view

After you create a weld or constraint, you should verify it's working the way you expect. Select the weld or constraint in the Explorer panel, and Roblox Studio will highlight it in the 3D view with a small visualization. For a weld, you'll see a small point showing where the connection is anchored. For constraints like HingeConstraint, you'll see a line or axis showing the direction of rotation.

Test your connection by moving one of the connected parts in the 3D view. If the weld is working, both parts should move together. If only one part moves, check that both parts are correctly assigned in the Part0 and Part1 properties. You can also run your game in Studio by clicking the Play button to see how the connection behaves during gameplay — sometimes a connection that looks correct in edit mode behaves differently when physics are active.

Troubleshooting connections that don't work

If two parts aren't staying connected, the most common cause is that one or both parts have Anchored set to true in their properties. An anchored part ignores welds and constraints — it stays in place no matter what. Check the Properties panel for each part and make sure Anchored is set to false. The exception is if you want one part to be completely fixed in space (like a wall or floor), in which case you anchor that part and leave the other unanchored.

Another common issue is that the weld or constraint is connected to the wrong parts. Open the Explorer panel, click on the weld or constraint, and check the Part0 and Part1 properties. Make sure they point to the parts you actually want to connect. If they don't, click on the property and select the correct part from the dropdown.

If parts are connected but moving strangely — rotating unexpectedly or drifting apart — the issue might be with the part's CFrame or Center of Mass. This is more advanced, but the quick fix is to make sure both parts have their origins (the point where their local coordinates start) in sensible places. For simple connections, this usually isn't a problem.

Frequently Asked Questions

Can I weld more than two parts together?

Yes, but you need multiple welds. Create one weld between Part A and Part B, then create another weld between Part B and Part C. Part A and C will both follow Part B's movement. You can chain as many parts as you need, but keep in mind that the more welds you use, the more complex your model becomes.

What's the difference between Weld and WeldConstraint?

WeldConstraint is a newer version of Weld that works more reliably with Roblox's physics engine. Both do the same thing — lock two parts together — but WeldConstraint is generally recommended for new projects. You can use either one; WeldConstraint just tends to be more stable.

If I weld two parts together, can I still move them separately in Studio?

No, once welded, they move as one unit in the 3D view. If you need to adjust one part's position relative to the other, delete the weld first, make your changes, then recreate the weld. Alternatively, you can select the weld in the Explorer and adjust its properties without deleting it.

Do welds affect how players interact with objects in my game?

Yes. If a player touches a welded object, both parts respond together. If you weld a door to a frame, the player can't separate them. This is usually what you want, but if you need parts to break apart under certain conditions, you'll need to delete the weld through a script when that condition is met.

What happens if I weld a part to itself?

Roblox Studio will let you create the weld, but it won't do anything useful. The weld will exist but have no effect. If you accidentally do this, just delete the weld from the Explorer panel.