Woodland Scenics Co
SubTerrain System Foam Accessories

Foam Putty(TM) 1 Pint
Walthers Part # 785-1447, p. 383 Walthers 2012 HO Scale Reference
A scale, $9.99, currently in stock at Walthers

 
This light-weight, nonshrinking filler putty dries with similar characteristics to foam. It's ready to use right from the jar and dries to a bright white color. Perfect for filling cracks between foam sections or small gaps and holes along the layout. Can be sculpted and carved while wet and sanded or carved when dry. Plastic jar comes with an economical 16 ounces of putty.