Simply using storyboard, constraints to set size of cell in UICollectionView
<p>Here's a UICollectionView, and the cell in purple:</p>

<p><a href="https://i.stack.imgur.com/BSUEY.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/BSUEY.png" alt="enter image description here"></a></p>

<p>Quite simply, I want the cells to be 1/2 of the collection view width.  (So TBC, it will be a two rows arrangement of cells in the collection view.)</p>

<p>(The collection view is simply fullscreen, so each cell is half the screen width.)</p>

<p>How do you do this in storyboard?</p>

<p>If I try to control-drag in the normal way, it basically doesn't work.</p>

<p>These are simple totally static cells (not dynamic). </p>

<hr>

<p>For anyone googling here, to save your time: Here's exactly (2016) the simplest way to make a two-across UICollectionView layout; no gaps between the cells.</p>

<pre><code>// Two - two-across UICollectionView
// use a completely standard UIViewController on the storyboard,
// likely change scroll direction to vertical.
// name the cell identifier "cellTwo" on the storyboard
import UIKit
class Two:UICollectionViewController
    {
    override func viewDidLoad()
        {
        super.viewDidLoad()

        let w = collectionView!.bounds.width / 2.0

        let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
        layout.sectionInset = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)
        layout.itemSize = CGSize(width:w,height:w)
        layout.minimumInteritemSpacing = 0
        layout.minimumLineSpacing = 0

        collectionView!.collectionViewLayout = layout

        // Note!! DO NOT!!! register if using a storyboard cell!!
        // do NOT do this:
        // self.collectionView!.registerClass(UICollectionViewCell.self, forCellWithReuseIdentifier: reuseIdentifier)
        }

    override func numberOfSectionsInCollectionView(collectionView: UICollectionView) -&gt; Int
        { return 1 }
    override func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -&gt; Int
        {  return 5 }
    override func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -&gt; UICollectionViewCell
        {
        return collectionView.dequeueReusableCellWithReuseIdentifier("cellTwo", forIndexPath: indexPath)
        }
    }
</code></pre>