Cutouts and Slots

There are numerous ways to indicate slots in various design tools, referred to as a “callout”.

Most callouts rely heavily on the Board Outline layer, so before attempting slots, it’s helpful to understand how your tool produces the board outline.

The callouts listed below are the “generic” callouts required for us to correctly understand a design. Not every design tool can produce a fully supported callout. Most can though, and it’s helpful to check our Design Tool Help pages for your specific tool if you encounter difficulty.

Officially Supported

Board Cutouts

Board cutouts are indicated identically to the Board Outline, but represent a region of the board to be removed instead of the outer edge..

We can guarantee correct fabrication of board cutouts that meet the following criteria:

  • Cutout dimensions exceed 0.1” x 0.1”.
  • No copper present beneath the cutout.
  • The board outline layer must contain only details pertaining to the board outline, cutouts, and slots.
  • Drawn with a Cutout Boundary, in which the centerpoint of the line indicates the fabricated board edge. Line thickness will be ignored.
  • The Cutout Boundary must be indicated by lines or arcs. Polygons, flashes, or other solid filled objects are not guaranteed to work correctly.
  • The cutout may contain text reading CUT OUT, but this is not required.

Cutouts and the appropriate renders

Note, currently renders for the board will not fully handle board cutouts. Paying close attention the the thin black lines of the Top preview, as well as the board outline will ensure that your cutout is detected for fabrication.

Typically, cutouts are cut with a 0.068” milling bit, for a 0.034” corner radius. Cutouts may be cut with larger or smaller milling bits however. The largest possible milling bit is 0.1”, which will generate a maximum corner radius of 0.05”.


We can guarantee correct fabrication of slots meeting all of the following criteria:

  • No copper present below slot
  • Have a width at least of 0.1” or larger

and drawn using one of the following supported callout methods

  • Uses Slot Path callout
  • Uses Slot Boundary callout with holes at each end
  • Uses Slot Boundary callout with a single hole

Previews of supported callouts

Nonplated slot using Path callout

Nonplated slot using Boundary callout

Nonplated slot using a single hole Boundary callout

Partially Supported

We cannot guarantee these slot types. They have a known, non-zero failure rate that prohibits us from providing a warranty on failures of these slot types. However, they can be typically fabricated without issue if the correct slot callout is used. The success rate for these slots is around 90%.

Because these slots may fail at random, it is advised to minimize their use, and whenever possible use a suppported slot or a via instead. This is especially important on high-value boards, or time-critical orders.

The following slot types fall into this category:

Small Non-Plated Slots

  • No copper present below slot
  • Has a width at between 0.04” and 0.1”
  • Uses any non-plated hole callout

Plated Slots

  • Copper present below slot and valid annular ring around slot.
  • Have a width at least of 0.04”
  • Uses any plated slot callout

Plated Slot Callouts

Plated slots can be indicated using any of the supported callouts.

Partially supported Plated Slot callout using a Slot Path

Partially supported Plated Slot callout using a Slot Boundary

Partially supported Plated Slot callout using a Slot Boundary and only one Drill hole

Not Supported

Slots indicated with other specs or callouts are entirely non-supported, and will not be fabricated correctly. This includes, but is not limited to, slots listed below.

Slots with unsupported specs

  • Slots width a width less than 40 mil

Slots using unsupported callouts

The following common slot types fall into this category.

  • G85 Drill Drag callouts.
  • G00+G01 Excellon drill milling instructions.
  • Drill files containing Gerber data to indicate slot information.

Our system will attempt to notify you if these slot types are detected. Closely examining the previews will help indicate if the slot matches an acceptable callout.

Most tools can convert these callouts to a supported method by simply drawing additional details on the board outline.

A typical slot indicated with a non-supported callout

Slots with overlapping drill hits

We do not support drawing slots with overlapping drill hits. Overlapping drill hits will typically be removed, leaving a single drill hit for your slot. If they are fabricated, slots generated with this method are of very poor quality.

Note that due to rendering limitations, overlapping drills may appear as a slot on the previews. This does not mean the slot will be fabricated correctly, however.

Slots drawn with ambiguous instructions

While not easily detectable by our automated process, certain types of callouts can confuse the semi-automated process used for fabrication. Common examples of these are below, but other confusing drawings may also fall into this category.

  • Slots boundaries that intersect the board edge. Whenever possible, these should simply be drawn as part of the board edge.
  • Slots along a board edge (typically for plated edges).
  • Slots drawn on a Board Outline layer that also includes significant junk data.
  • Slot Paths drawn in a closed shape, such as large square cutouts. In these cases the drawing can be interpreted as a Slot Boundary for a cutout region instead, and will be the incorrect size.
  • Slot Paths that would require the addition of tabs to safely fabricate. This mostly occurs on panelized designs that do not follow our panelization guidelines.
  • Small circular cutouts, such as non-plated holes or mounting holes. Instead, use a proper Drill callout from your tool.

Replacing Slots with Drills

When possible, in many cases slots can be avoided by simply using drill hits. Replacing the non-supported feautures with a slot will guarantee consistent and correct fabrication.

Example of a footprint using Holes instead of slots