How do I model mirrored

I am constructing an object supposed to be identical on both sides of the axis, by te way the y axis - when I watch tutorials on Youtube, they all used this consept but never said how. I’m a total newb btw. I am contructing a tarp for covering a hammock, a plane with added vertices that must be split dead center(the y axis)

I need to model an advanced tarp canvas functiong as a ceiling for a hammock.
Anyway, I need to have whatever adjustment I make to be mirrored, just like most tutorials on Youtube.
And the preferred axis of centre would the Y. I’m sure it’s easy, I’m just a total newb…and how do I add vertices to the plane to construct the shape? Thanks

How to mirror round the Y axis
Mirror modifier set to Y axis

Model half the object and use a mirror modifier. The modifier allows you to mirror around the X, Y or Z axis. Also a good idea to check the box called clip within the modifier. There should be youtubes on the mirror modifier.

Read more here about the modifier.

Select your object.
Select the Modifiers icon at the top of the Properties editor.
Add the Mirror modifier.
In the modifiers panel that comes up, select the axis you want to mirror.
Select the Clipping checkbox in the modifiers panel.
Select the little upside-down triangle icon at the top of the modifiers panel if you want to see the mirroring while you’re in edit mode.

That should do it!

There is one such plane already ready to go. It’s called ‘Grid’ and you can find it in Add list little below the Cube. Use W-> Subdivide or Ctrl-R in edit mode on a simple plane.

All objects you add initially have their centers - Origins - right in a middle, they are symmetrical and Mirror modifier would not show up clearly if you add it. It’s there but all vertices are on top of each other still.

Add Mirror modifier and either move all vertices in Edit mode on axis you added mirror or delete half of existing verts - this will be recreated by Mirror modifier. As soon as you press Apply on modifier tab while in Object mode all verts get “real” again; do not Apply until you really need to.

To mirror your geometry do the following steps. I added some screen shots to help you get started…

  1. In Edit mode create the geometry that you want to mirror.
  2. While in Edit mode add a Mirror Modifier. Be sure to select only the axis that you want to mirror. In my example I selected the Y axis only. You most likely want to also check Clipping.
  3. At this point you can keep working on your geometry and it will get mirrored.
  4. When you are all done editing your geometry go to Object mode and then Apply the Mirror Modified. At this point your geometry will become one object and you now have an symmetric object. If you modify the geometry after applying the mirror modifier it will no longer get mirrored.

I hope this helps you.