When editing a support via the equipment editor in the 'Configure' window, the 'Edit Support' window gives you the following options. If you want to follow the full process for adding equipment to a structure, please see the following articles:
RECOS: Allows you to adjust the RECOS in metres. Changing this value will also affect the reach.
Reach: Allows you to adjust the reach in metres. Changing this value will also affect the RECOS. This option will only be available when editing a catenary wire point.
Please note: When adjusting the RECOS or reach of portal structure masts, these values can only be adjusted using the up/down arrows to ensure your gantry length is valid.
Length: Change the support (i.e. mast) length in metres. This value can only be changed using the up/down arrows to ensure your mast length is valid. Please note, if you are editing an attachment point, this value will not be editable.