Bootlace ferrules are small, cylindrical connectors that are used to terminate the end of a wire or cable. They are typically made of metal with a colored plastic shroud for the incoming wire.

Ferrules are designed to provide a secure, reliable connection between two wires or between a wire and a device. The purpose of a bootlace ferrule is to protect the wire from damage, to improve the wire’s electrical conductivity, and to ensure that the connection between the wire and the device is mechanically stable.

Bootlace ferrules are commonly used in a variety of electrical and electronic applications, including telecommunications, aviation, and automotive systems. They are named for their resemblance to the laces on a boot, due to the way they are crimped onto the wire to hold them in place.

In most 3D printer applications,  ferrules are commonly used in terminal blocks and 3d printer mainboards that have screw connectors. Hotend heater connectors are a prime example:

Wires crimped with bootlace ferrules for a hotend heater connection on the Octopus Pro.

Ferrule crimped wire connected into a Wago through terminal block.