Most toilets use standard sized toilet tank bolts. If the bolts that attach the tank assembly to the bowl are not standard sized, though, you will have to use alternative bolts. You can do this by taking the old bolts to the local hardware store with you. Check the nuts and bolts aisle for new bolts in the necessary size. Compare the old bolt to the new ones to be certain that they are the same size. Any size difference can cause problems. If the new bolts are too large, they will be unusable. If they are too small, then leaks may occur, so sizing properly is important.