Inserts come in loads of different shapes and sizes. I’m going to run you through some of the ones I have in my stash. They all effectively do the same job and the shape makes little to no difference on the performance.
For some inserts you can adjust the way you use them to get better performance, where this is the case I have added additional photos.
The most common of all inserts. This is just used as is. It will normally fit which nappy it came with extremely well, but you’ll find these a very universal fit for most nappies.
The vast majority of pocket nappies come with a standard rectangle inserts.
As the name suggests this insert is shaped like an hourglass. It gives a bit more width at the front and back, going narrower between the legs. This is also used as is. Some will have poppers if they are part of an Ai2 nappy.
This is basically a long piece of fabric which is the width of the nappy.
The temptation is to just fold this insert in half. That will probably fit the length of the nappy nicely. This will give you two layers of absorbency. But by adjusting the fold slightly we can give an extra layer of absorbency, in the right place, improving the performance. I call this the Z-fold.
Kind of a cross between the hourglass and the snake. This is a longer insert that fans out at one end. It will be too long for the nappy and will need folding.
Depending on the thickness of the insert you could try folding it in the Z-fold like the snake insert above. If the insert is too thick, or you just fancy folding in half anyway, then you can still target the absorbency. For a boy, or tummy sleeper, I put the wider part at the front as it will provide more absorbency, for a girl I’d put the wider part at the back.
A trifold is a flat piece of fabric, they are rectangular in shape but more square than a normal rectangle insert. Just like a prefold. These are designed to be folded into thirds to create that standard rectangle shape. The reason they are able to be unfolded is to speed up drying time. Rather than sandwiching several layers of fabric together these allow those layers to be separated. The downside of this is the insert tends to be a bit bulkier. You can read more about trifolds here.