Hi Explorer, thanks for the question. When installed correctly, and in conjunction with other handrail brackets, these rail brackets will hold 250lbs of direct, downward pressure. Thank you.
3" to fit under the rail !!
Check your wall stud spacing //16" on center is normal // depending on how long the rail is that you will be installing -- space the bracket // I used two brackets on a 5' rail
install the brackets to the wall studs // 16" on center or double the space to 32" // you need the support and a solid mount ( wall stud ) for a solid foundation !!