Hi
Found out my bitch is in pup :))
My dad is building our whelping box as he is a carpenter and wants to do it.
Can someone tell me the height of the rails from the floor and from the edge in too
Thank you
Too add it's a medium breed dog

My husband made our whelping box, based on one we'd seen.   It consisted of two sections, 4 X 4, with a floor so they were up off the ground.   The pig rail was only round 3 sides of one section, roughly 4" and 2" wide and solid, not a pole. 

We used the 4 X 4 section to begin with, the sides being around 3' high with the front about 4" (from memory, it might have been higher) so mum could get in but not the puppies at that stage, out.   Bearing in mind we had Bassets so the access couldn't be too high, for mum.  

The second 4 X 4 section, with the same height floor,  had no pig rails but the front had a hinged door for mum's access.   Once in use, the front of the first section was removed and the second section pushed up against the first.   This gave a big (8 X 4) box.   Obviously the first section was the 'sleeping' end and the second more the 'toileting' end.   The sleeping end had a right angled gallows, for the brood lamp which kept that area nice and evenly warm - and dry.