This little piece of notched plastic is a Resistor Lead Bending Tool. Sometimes referred to as a ”forming“ tool, this little guy provides you with an easy and reliable way to get the exact distance between two resistor leads that you need to PTH soldering.
The Resistor Lead Bending Tool is two-sided, with one side offering 0.4"-1.5" spacing for ¼ Watt resistors and the other side offering 0.5"-1.5" spacing for ½ Watt resistors.

At SparkFun they use a lot of ¼ Watt resistors in their PTH soldering kits and have found that this tool is very handy when soldering a lot of resistors at once or over a longer period of time.
To use this tool, simply insert your ¼ Watt or ½ Watt resistor into the desired spacing groove and bend the leads over the edges. It’s that simple!

Note: 1/6 Watt resistors and specific diodes can be used on this tool but you will need to make sure they are centered before attempting to bend them to your desired preference.

Features:

• ¼ Watt Resistor Spacing: 0.4"-1.5"
• ½ Watt Resistor Spacing: 0.5"-1.5"
• Made from high impact ABS Plastic