What sole custody means
Sole custody means one parent holds custody alone, and like custody generally it splits into two kinds. Sole legal custody gives one parent the authority to make major decisions without needing the other's agreement. Sole physical custody means the child lives primarily with one parent. A parent can have one form of sole custody without the other.
A frequent misconception is that sole custody cuts the other parent out entirely. Often it does not: a parent without custody may still have significant parenting time, and courts generally favor a child's continued relationship with both parents where it is safe. The label describes authority or primary residence, not necessarily the amount of contact.
For documentation, sole arrangements still benefit from careful records, whether to show that you are exercising your responsibilities well or to document concerns that bear on the arrangement.
Example: even with sole physical custody, keeping a record of the other parent's scheduled time and how it goes matters if the arrangement is ever revisited. What sole custody grants varies by state, so rely on the specifics of your order.