How to create duplicate vertices on both sides of an object?

Hey guys, new here as well as to blender and 3D modeling as a whole, and while doing some practicing with a model and a reference picture of a sword I thought would be good to practice with, I’ve run into something I can’t find any info on how to do: How to make duplicate vertices on two or more sides of an object to make it symmetrical? Or would I be better off creating a new object to act as a ‘piece’ to the sword?

@Sanoka
The mirror modifier would probably be what you are looking for. In order to use it right you would have to split your model in edit mode directly down the center then in the properties panel you can select modifiers and then select mirror. Enable clipping so that the center verticies do not separate while modeling. Then whatever you do to one side of the mesh it will also do to the opposite side.

Side note that if there is non symmetrical shapes those can’t be added while using the mirror modifier so in most cases all the symmetrical modeling is done with the mirror modifier then once finished and happy with the base shape then you can apply the mirror modifier and now you can edit non symmetrical shapes without them being duplicated to the mirrored axis.

@Sanoka Here is a quick video I did to show the mirror modifier in use in case my description was a little too confusing. Hopefully it helps, my mic is not working so there is no audio but I enabled screencast to show keystrokes.