My advice as usual is to go for quality. After taking professional advice I chose Middle Atlantic racks. A lot of racks are not actually very well made, or handy. I chose form
this series of their racks.
These racks are strong and well made. They make powering easy and straightforward. They also make grounding easy, You can easily bond equipment to the racks.
Yes, rack mounted equipment is mounted from the front, with standard mounted spaced holes. Equipment is designed in multiples of that standard spacing.
The hole spacing for standard 19-inch racks on the mounting flange is
spaced in groups of three holes. This three-hole group is defined as a Rack Unit (RU) or sometimes just call a “U”. 1U occupies 1.75 inches (44.45 mm) of vertical space.
You need to buy the black threaded rack screws to mount the equipment. These are made of strong high grade steel are very strong and have the standard rack thread.
You can put in shelves also. These can be bought or you can make your own. You can also mount equipment the faces front and back. For instance my ethernet hubs and the patch bay face backwards. If you are going to use a UPS, these are heavy. So you mount them at the bottom of a rack, and do use support under them.
These are my three Middle Atlantic racks
You can put other cabinetry between.
Powering is made easy.
One of the hubs and the patch bay facing the back of the rack.
For non pro and therefore non rack mounted equipment the spacing in not in Rs, so you need to make spacers. I used finished wood oak veneered.
You can see the non R units mounted on MDF shelves.
The standard spaced equipment can be mounted and the rack closed with pro R spaced spacers.
As always grounding is crucial.
That really covers the basics. If you have more questions, and you probably will, I will do my best to answer them. Using pro racks has enormous advantages and is the basics of building complex systems that are quite with excellent SNR. They are one of the foundations of superior systems.