Modo: closing holes

1. Being in items mode, select the item. 
2. Pressing ctrl key, turns edges mode button to boundary button. Holding ctrl key click on boundary button. This displays open polygons count on the lower left side of the viewport as first line. 

To close open polygons:
 

1. On the right side displayed panels, Select Lists tab, statistics tab -> edges -> by boundary -> geomtry. 
2. Geomentry displays how many edges are open and how many are selected. Uless you closed some of the eges using the 4th step, both numbers would be same.
3. Click on the plus icon displayed before the geometry option so that it highlights in white color. Geomentry calculates how many edges are open and how many are selected. Unless you closed some of the eges using the 4th step, both numbers would be same.
4. Place mouse ponter on the view port and press p key. This tries to close the open edges.
5. Click on the view port to unselect the selected eges.
6. Repeat steps from 3 till Geometry displays 0 count.