Problem when subtracting

[liinanotko]

 Hi! I struggle with this problem. I am trying to make windows and when i subtract the boxes it subtract it only from one side. The box is bigger than the wall and i can see the lines on both sides. Any help please?

[Kent1Cooper]

If the "sides" you speak of are separate 3D Solids, and the wall is not monolithic, did you select both of them [or all of them if more than two parts make up the wall] at the "Select solids, surfaces, and regions to subtract from .." prompt(s)?

[liinanotko]

Hey, yes I selected both sides. 

[leeminardi · Accepted solution]

When using subtract it is good practice, when feasible, to have the solid that is going to be subtracted to fully penetrate the solid that is to remain.  That is, make sure the box you are subtracting is not flush with the wall but passes through it.