# M3 Hardware
## M3 Hardware Basics
The REV DUO build system uses [M3 hardware](https://www.revrobotics.com/ftc/hardware/fasteners/) to connect, or fasten, brackets and structure together on a robot. Different applications require different length screws. When attaching a bracket to extrusion, shorter screws are generally required. Use longer screws to connect Control System components and other thicker materials.
{% hint style="info" %}
*See the* [*“Tips and Tricks”*](/duo-build/building/tips-and-tricks.md) *section of this guide for best practices when working with the M3 Hardware.*
{% endhint %}
## Tools
We include all the tools needed to use the parts in the FTC Starter Kit. Take a moment to identify the tools below:
* 5.5mm Nut Driver ([REV-41-1119](https://www.revrobotics.com/rev-41-1119/))
* 5.5mm Combination Wrench ([REV-41-1374](https://www.revrobotics.com/rev-41-1374/))
* Allen Wrench Pack (1.5mm ([REV-41-1376](https://www.revrobotics.com/rev-45-1882/)), 2mm ([REV-41-1377](https://www.revrobotics.com/rev-41-1377/)), and 2.5mm Allen Wrenches)
* \#25 Chain Tool ([REV-41-1442](https://www.revrobotics.com/rev-41-1442/))
As robots become more complex, there are additional tools, hardware, and fasteners available on the REV website:
* 5.5mm Ratcheting Combination Wrench ([REV-49-1711](https://www.revrobotics.com/rev-49-1711/))
* Metric Step Drill ([REV-49-1455](https://www.revrobotics.com/rev-49-1455/)) for drilling holes of different sizes
* Zip Ties ([REV-41-1161](https://www.revrobotics.com/rev-41-1161/))
* Hook and Loop Fastener ([REV-41-1373](https://www.revrobotics.com/rev-41-1373/))
* Variety of replacement screws, and additional screw lengths
## T-Slot Screws
Another type of hardware included in the kit is the T-Slot Screw ([REV-41-1907](https://www.revrobotics.com/rev-41-1907-pk25/)). These screws have a T-shaped head allowing them to drop in the slots of the [Extrusion](https://www.revrobotics.com/ftc/structure/15mm-extrusion/) or[ C Channel](https://www.revrobotics.com/competition/ftc/structure/channel/). This allows for modification of an existing design by adding in brackets and structure without needing access to the end of a slot.
{% hint style="warning" %}
Even though T-Slot Screws are convenient, it is always recommended to use full Hex Head Screws because they are a stronger fastener.
{% endhint %}
### Product Specs
* Material: Corrosion resistant zinc plated steel
* Length: 8mm
## How to Use?
Simply drop the t-slot screws into the channel where you want them to go and attach the brackets or structures you want and tighten until [snug](/duo-build/building/tips-and-tricks.md#snug-not-stuck).
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