# Place an object

Move a grasped object to a target location and release it.
> Source: https://docs.viam.com/motion-planning/move-an-arm/place-an-object/


Placing is the mirror image of picking, but with a different failure mode:
releasing the object is the moment you lose control of it. A placement that
lets go too early drops the object; one that descends too far jams it into
the surface. This guide walks through a four-step placement that controls
those two failure modes: move to a pre-place pose, descend to the placement
surface, release, and retreat straight up so you do not disturb what you
just set down.

## Prerequisites

- Object already grasped (see [Pick an object](/motion-planning/move-an-arm/pick-an-object/)).
- Placement location known in world coordinates.

The code below continues from [Pick an object](/motion-planning/move-an-arm/pick-an-object/);
`motion_service`, `gripper`, and `world_state` are already defined in that script.

## Steps

### 1. Move to pre-place position




### Python

```python
# Pre-place: above the target location
pre_place = PoseInFrame(
    reference_frame="world",
    pose=Pose(
        x=500, y=0, z=200,
        o_x=0, o_y=0, o_z=-1, theta=0
    )
)

await motion_service.move(
    component_name="my-arm",
    destination=pre_place,
    world_state=world_state
)
```



### 2. Descend to the placement surface

The descent pose puts the object where you want it to end up.
`SURFACE_HEIGHT` is the world-frame z of the placement surface plus the
distance from the arm's end effector to the bottom of the held object (the
grasp offset plus the part of the object below the grasp), so the object's
bottom touches the surface at release. For a known surface, measure once and
hard-code it. For a detected surface, set it from the vision result.




### Python

```python
# Place: at the surface.
# Set z to the height of the placement surface in your workspace.
# For example, if you detected the target location, use its z coordinate.
SURFACE_HEIGHT = 50  # mm: surface z plus the end-effector-to-object-bottom distance
place_pose = PoseInFrame(
    reference_frame="world",
    pose=Pose(
        x=500, y=0, z=SURFACE_HEIGHT,
        o_x=0, o_y=0, o_z=-1, theta=0
    )
)

await motion_service.move(
    component_name="my-arm",
    destination=place_pose,
    world_state=world_state
)
```



### 3. Release and retreat




### Python

```python
# Open gripper to release
await gripper.open()
print("Object placed")

# Retreat: lift straight up
retreat_pose = PoseInFrame(
    reference_frame="world",
    pose=Pose(
        x=500, y=0, z=200,
        o_x=0, o_y=0, o_z=-1, theta=0
    )
)

await motion_service.move(
    component_name="my-arm",
    destination=retreat_pose,
    world_state=world_state
)
print("Retreated from placement")
```



## Tips

- **Keep the object level on the way down.** A carried object with an open
  top (a cup, an open box) spills if the gripper tilts during descent. Add an
  [`OrientationConstraint`](/motion-planning/move-an-arm/constraints/),
  which locks the end effector's tilt, with a tolerance of 3 to 5 degrees
  for the descent segment; remove it for the retreat.
- **Retreat straight up.** Any lateral motion during retreat can catch the
  object the gripper just released. Plan the retreat pose with the same x
  and y as the place pose and only the z raised.
- **Update `WorldState` after release.** The placed object is now a static
  obstacle. If the next motion passes near the placement location, add a
  `Geometry` matching the placed object to a `GeometriesInFrame` entry in
  `WorldState.obstacles` so the planner routes around it.

## What's next

- [Pick an object](/motion-planning/move-an-arm/pick-an-object/):
  the pick half of the pick-and-place workflow.