# Field mappings & transformations (services)

## Introduction 

Mappings are at the heart of Patchworks.

When we pull data from one system and push it into another, it’s unlikely that the two will have a like-for-like data structure. By creating mappings between source and destination data fields, the Patchworks engine knows how to transform incoming data as needed to update the destination system.

The illustration below helps to visualise this:

![](/files/dVnIlP92nVrNiq5Uec8W)

Mappings are defined within Patchworks [services](/product-documentation/patchworks-services/getting-started/what-is-a-service.md). With its **standard** **connectors**, Patchworks knows what mappings are likely to be between two given systems - default mappings are provided and can be tweaked if needed.

{% hint style="info" %}
If your organisation has in-house development expertise and complex transformation requirements, you can use our [custom scripts](broken://pages/oZoHN71i3KN7FMkgdP1x) feature to code your own scripts for use with field mappings. 
{% endhint %}


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