I have a brick colonial built in 1988. The window sashes are four over four, single pane, wooden sashes, in which the bottom (movable) sash slides in a vinyl track. The upper sash is fixed. On many of the windows, the bottom sashes are so loose in their tracks that they will not stay up when raised. The windows themselves are in great shape, but there is no way to keep them open unless they are propped open. I had settled on placing wooden dowels in the tracks to prop them open. This worked well, and was unobtrusive, and (I thought) would not be noticed by my two year old twins. Well, my curious, busy handed son, did notice the dowel and pulled one out. The window sash came crashing down, and luckily did not fall on his hand. But, I got lucky this time. Does anyone know, or can offer any advice about how to repair or retrofit these windows that are in good shape, but will not stay up? Thank you in advance.