What an Object Exposes

6 min readUpdated Aug 2026

Mark the geometry a consumer is allowed to grab: select it in the base sketch and press w. That is the first of exactly three handles someone placing your object gets, alongside the docking anchors you drew and the parameters you exported. Everything else you built is private plumbing. This article covers the first two; Choosing the Parameters You Expose covers the third.

Exported geometry is what a consumer can grab

Select one or more primitives in the base sketch and press w, or use the Toggle exported chip on the toolbar or in the radial menu. Exported primitives turn magenta so you can see the interface at a glance.

The chip appears only while the base sketch is active. In any other sketch of the object it is not offered, because exporting geometry from a sketch that never touches the host has no meaning.

What exporting does is not cosmetic. At placement time every exported primitive is materialised into the consumer's document as real sketch geometry belonging to their placement. They can drag it, dimension it and constrain it like anything they drew themselves, and it is what drives the position controls in the placement popover.

So choose the geometry that describes where the object goes, not the geometry that describes what it is. A bolt-pocket object exports the circle at the centre of the pocket. It does not export the counterbore outline, the chamfer construction lines or the eight points you used to lay out a pattern: those would land in the consumer's sketch as clutter they cannot delete.

The origin point is created exported for you, and it does not count. Every check for "does this object export anything" ignores it deliberately, since otherwise every object would pass.

Docking anchors say where the object seats

Two objects that mate need more than a position. In a sketch of the object, the toolbar shows a DOCKING group with two tools:

Container, described as Docking container (socket) — accepts a component of the same tag.
Component, described as Docking component (plug) — snaps into a container of the same tag.

Both place exactly like a construction point, with the same snaps and the same constraints, so an anchor can be dimensioned into position like any other sketch point. The group is present in any sketch of a smart object, not only the base sketch, and it disappears entirely in a plain model.

That matters more than it sounds. Because a sketch carries a plane, an anchor is a point plus a direction, not only a coordinate. Draw one on a sketch 12 mm up the side of a boss and the mate seats there, in that orientation. You are not confined to the face the object lands on.

Matching is directional and literal: a component seeks a container, and the two mate only when their tags are identical. Two containers never mate, and neither do two components.

The Anchors window

Hover the Anchors icon in the column at the top right of the viewport and its window slides out to the left. It is there only while you are editing a smart object, because a plain model has no anchors of its own. Inside is every anchor in the object, across every sketch, sorted containers first and then components, each row carrying a role glyph, an eye toggle, the pairing tag and a delete.

The tag is editable by double-clicking it, and the window says why it exists: The pairing tag: a container and a component with the SAME tag snap together. Double-click to edit. New anchors start on the tag global, which is fine for an object with one seat and wrong the moment an object has two kinds of seat. Give tags names that describe the joint, not the part: lid-post, rail-40, m3-boss.

The field is called Tag and never Name, and the distinction is deliberate. Renaming is how you break a pairing: change the tag on the container and every component that used to seat there stops seating, in every document that already placed it. Pick the tag once, at the start.

An object with nothing drawn yet reads No docking anchors yet. Draw one with the DOCKING tools in a sketch.

Required link

The window carries one toggle, Required link, described as This object can only be placed docked: at least one of its components seated on a compatible container. Turn it on for an object that has no meaning free-floating: a shelf pin, a rail carriage, a lid that is nothing without its box.

The toggle is disabled until the object has at least one component anchor, with the tooltip Needs at least one component anchor — without one there is nothing to dock. Containers alone will not do, because a container is a seat offered rather than a seat taken.

The rule relaxes itself rather than trapping anyone. Delete the last component anchor with the flag still on and the object stops requiring a dock. That is kinder than an object nobody can place, but it means the flag is not a guarantee you can rely on: check that the component anchor is still there.

Understand what you are turning on before you do. For a consumer, Required link means the ghost floats red and clicking does nothing until they find a compatible seat, with no message explaining why.

Nothing checks your interface

An object with no exported primitives, or one that never modifies the host, saves happily and publishes happily. It then cannot be placed, and nothing on screen says why. The rules exist; no screen enforces them.

Which makes the checklist yours:

At least one primitive other than the origin is exported in the base sketch.
At least one feature actually modifies the host body. An object that adds nothing and cuts nothing produces no result on the consumer's part.
Every anchor has a tag you chose on purpose.
The object has been placed, once, in a different document. That last step catches the other three in about a minute.

When it fails

The Toggle exported chip is greyed or missing. Either you are not in the base sketch, or your selection is only the origin point. Select real geometry in the base sketch.

The object places but there is nothing to grab or dimension. No exported primitives. Go back to the base sketch and export the geometry that locates the object.

Two objects refuse to dock. Compare tags character for character in both Anchors windows, then check roles: one side must be a container and the other a component.

The dock seats in the wrong orientation. The anchor's sketch plane sets the direction. Move the anchor to a sketch whose plane faces the way the joint should close.