On Tue, 14 Jul 2015 18:40:32 -0400, wrote:

On Tue, 14 Jul 2015 17:43:23 -0400, micky
wrote:

On Tue, 14 Jul 2015 12:23:31 -0400, wrote:

On Tue, 14 Jul 2015 00:54:03 -0400, micky
wrote:

On Mon, 13 Jul 2015 20:55:44 -0400, wrote:

On Mon, 13 Jul 2015 16:44:40 -0700 (PDT), TimR
wrote:

On Monday, July 13, 2015 at 6:12:47 PM UTC-4, Boris wrote:
Hi,

We're remodeling and the old flooring (lino and carpeting) has been taken
up to install hardwood. I noticed many of the 4'x 8' x 3/16" underlayment
plywood has lines of stitching. Yes, stitching, which goes through to both
sides, and is made of nylon or cotton multi-strand thread.

What is this? I've never seen it before.

TIA

Very common in boatbuilding to stitch plywood then epoxy over, but I've not seen it on a floor.

What's the purpose of this? Doesn't the glue hold it together.

I've never seen plywood underlayment stitched, but "fingerjointed
hardwood "or "fingerjointed parquet" is often stitched with nylon
cord.

Same question?

Does "self jigging" ring any bells???

No but I looked it up. Was the stitching put in before the glue set?
In the fingerjoint flooring and in boat building - most definitely.
In boat building, the whole boat gets stitched together before any
gluing/resin application .
The stitching holds everything in position for gluing AND it
re-enforces the glue joint.

Very interesting. It's a good thing I learned this before I built my
boat.