When you work on a model, you might often work with elements that are checked out in writeable units but that other unitsreference in a read-only state.
当您处理一个模型时，您可能会处理检出为可写单元但是其他的单元参考在只读状态的元素。
3
The name is a reference to International Prototype kilogram, as a base unit of mass in the International System of Units.