Yes. You can use them with conduit or tubing. In fact, a
reference to this practice is made in 314.16(C).
It's an elbow fitting intended to enable installing of the raceway; the
contained conductors cannot contain splices, taps, or devices [314.16(C)].
Twice the cross-sectional area of the largest conduit or tubing to which it can
That would be the maximum number permitted for the conduit or tubing to which it
is attached, per Table 1 of Chapter 9 [314.16(C)].
In a rigid and secure manner [314.16(C)]. Typically, a conduit body has screw holes or screw flanges for this purpose. Screw or bolt the conduit body in place. The conduit or tubing cannot
serve as the support; you run conduit or tubing from securely mounted box or
body to securely mounted box or body.