Dumb question
 

I'm planning to use the Pellon grid interface to cross hatch, 1in. grid . Here's the dumb part. Where do you layer the interface ? Is it removable when you are finished ?

Not sure which Pellon product you are planning to use, but if it is Quilter's Grid, it is meant for piecing. It becomes part of the interior of the quilt. You would not use it for cross hatching after the quilt sandwich has been put together.

I'm new to quilting; but i believe the interfacing is intended to be left in between 2 layers of fabric.
I think you would place it (or could fuse it, if using fusible) to the wrong side of a fabric.

Crosshatch
 

What you might do instead is use a diagonal plaid fabric for the backing. Quilt from the back rather than the front, following the plaid lines as quilting lines.

I crosshatch with painters tape.
I draw the first line with erasable ink.
Then I cut two six-inch pieces and I alternate them as I move down the parallel line to sew the rest of the quilt.
It is very easy and I love how it looks afterwards.
Sometimes I use a 1.5 inch tape and sometimes I use a 1 inch tape.

I was going to suggest the same thing as klarina. It's sooooo easy to use the painter's tape and goes really quickly.

I do the same thing as Karina and DonnaC - The green Painters tape is so easy to use and comes in different widths. Very easy to use and also to remove or adjust.

great idea