---
title: NSCollectionLayoutBoundarySupplementaryItem
framework: appkit
role: symbol
role_heading: Class
path: appkit/nscollectionlayoutboundarysupplementaryitem
---

# NSCollectionLayoutBoundarySupplementaryItem

An object used to add headers or footers to a collection view.

## Declaration

```swift
class NSCollectionLayoutBoundarySupplementaryItem
```

## Overview

Overview A boundary supplementary item is a specialized type of supplementary item (NSCollectionLayoutSupplementaryItem). You use boundary supplementary items to add headers or footers to a section of a collection view or the entire collection view. Each type of supplementary item must have a unique element kind. Consider tracking these strings together in a way that makes it straightforward to identify each element, for example: Add boundary supplementary items to a section by setting that section’s boundarySupplementaryItems property:

## Topics

### Creating a boundary supplementary item

- [init(layoutSize:elementKind:alignment:)](appkit/nscollectionlayoutboundarysupplementaryitem/init(layoutsize:elementkind:alignment:).md)
- [init(layoutSize:elementKind:alignment:absoluteOffset:)](appkit/nscollectionlayoutboundarysupplementaryitem/init(layoutsize:elementkind:alignment:absoluteoffset:).md)

### Specifying scrolling behavior

- [pinToVisibleBounds](appkit/nscollectionlayoutboundarysupplementaryitem/pintovisiblebounds.md)

### Specifying position

- [offset](appkit/nscollectionlayoutboundarysupplementaryitem/offset.md)
- [alignment](appkit/nscollectionlayoutboundarysupplementaryitem/alignment.md)
- [extendsBoundary](appkit/nscollectionlayoutboundarysupplementaryitem/extendsboundary.md)

## Relationships

### Inherits From

- [NSCollectionLayoutSupplementaryItem](appkit/nscollectionlayoutsupplementaryitem.md)

### Conforms To

- [CVarArg](swift/cvararg.md)
- [CustomDebugStringConvertible](swift/customdebugstringconvertible.md)
- [CustomStringConvertible](swift/customstringconvertible.md)
- [Equatable](swift/equatable.md)
- [Hashable](swift/hashable.md)
- [NSCopying](foundation/nscopying.md)
- [NSObjectProtocol](objectivec/nsobjectprotocol.md)

## See Also

### Appearance

- [NSCollectionLayoutSupplementaryItem](appkit/nscollectionlayoutsupplementaryitem.md)
- [NSCollectionLayoutDecorationItem](appkit/nscollectionlayoutdecorationitem.md)
- [NSCollectionLayoutAnchor](appkit/nscollectionlayoutanchor.md)