Pretty nearly impossible to accomplish an actual repair to splits (I take it you mean the panels) without disassembling. To get any glue to hold, the surfaces have to mate up closely and be clean. Hopefully these aren't old cracks that are full of paint, caulk and dirt. I have sometimes had success by striking the "raise" molding of the panel with a hammer and block of wood to free up the halves of the panels from their plowed slots in the sticking of the door. This allows the gap to be widened temporarily while I clean out the debris. Then the panels are brought together. I lay the door flat and apply tape to the underside of the crack, to prevent the glue from running out. If need be, small blocks for clamps can be hot-glued to the surface along either edge. I use epoxy for these repairs. Try not to glue a panel into the frame; stop the glue short of the ends. When the glue is cured, the excess can be scraped and sanded off. If you mean surface checks in the sticking of the door, then these are seasonal and may close on their own in summer. At that point, having the door fully sealed will prevent the from opening up every winter. Casey

randy- I have often used a similar method to what you are suggesting when trying to mask a flaw in one of my woodworking projects, but, in this instance, I think the gaps are small enough that just filling them with as close a match of wood filler as possible may produce adequate results, The OP could always try filling the cracks first, and then move on to your more sophisticated suggestion if unhappy with the first approach.

Hopefully that is an impact crack and not a problem with the subfloor. Removing and replacing the tile is the way to make it look "perfect". So long as the edges aren't dangerous, cracked tiles are welcome to be left in place (until they become dangerous). The grout on that tile also needs repair. I would check the entire floor to ensure you are not seeing the beginning of a failing tile floor. Failing tile can be seen with ++ cracked grout or multiple tiles that are looking stressed (fine cracks in the body of the tile that have yet to crack all the way through like the tile you show in your photos). A quick inspection of the entire floor will tell you whether or not a repair is even worth it. A tile floor that is in the beginning stages of failure is not worth repairing. I'm hoping Joseph will pop by to offer any suggestions for "filler" that might be used to correct the tile without removing/replacing. I'm a wood/cork flooring pro...which means tiles and stone are not my strong point.

Thanks everyone! I won't be able to do this until Fall, since I have a huge waterlily growing in it. The crack is small and the leakage is minimal so far. I'll keep my eye on it and if it gets worse, I guess I'll have to figure out what to do with this huge waterlily (and the million tadpoles that live in the tank). If I can wait until later Fall, after the stocktank is drained, would it be better to do it early next spring, so it doesn't live through winter first? I wonder what causes these cracks.....might it be manipulating this big stocktank to turn it over in winter and then back up again in spring........or could it be a slight unevenness when it's full? I'm sure the sun is hard on it too. I have 2 in-ground 300 gallon stocktanks and (knock on wood), they've been leak-free for at least 15 years. But that's probably because of never being moved or exposed to the sun. I'm going to print off all your suggestions so I have easy access to them when the time comes. I really appreciate everyone's suggestions!