Unable to weld,bridge vertices or edges


I have been trying to follow some steps to make an AK 47 in 3ds max but when I try to make an sight to match the surface/edges of the weapon object it doesnt let me weld or weld target, bridge vertices or edges neither I can cap the gap between vertices which were weld

some images of the object imgur . com/a/NTs8JJ5

Solution Edit:

Deleted both faces of the objects (lower face from the sight and upper face of the sight’s support) and bridged edge by edge and now I was able to join them

now I wonder can I fill the hole where the faces where?