A free mod for Valheim, by Jere Kuusela.
Ruler is a powerful measurement tool. It adds a new command to the game to measure and visualize distances. It works like a real ruler, but you can use it from anywhere.
In addition to that, you can configure the settings to your needs. For example, you can use it with or without the 3D option, you can set the color of the ruler, you can choose whether to draw the axis lines or the ruler, and you can choose the distance unit. It's very easy to use. Just install the BepInExPack Valheim, download the latest zip, and you're ready to go.