When both parts have clearance holes, when nothing should project, and when a part with no orientation is worth having.

Two clearance holes and a screw from each side is the simplest arrangement, and it needs no thread in either part.

Nothing projects from either end, so a dismantled assembly has no studs standing proud to catch or bend.

The part is symmetrical, so it cannot be fitted the wrong way round - useful in repetitive hand assembly.

The trade-off is two screws instead of one, and two chances to get the length wrong.

For building a stack rather than setting a single gap, male-female standoffs chain more neatly.

They bottom out inside the standoff and clamp nothing, while feeling perfectly tight.

Most female-female standoffs are blind-tapped from each end, with solid material or the other screw in the middle.

A screw that reaches that point stops turning, and the resistance is easily mistaken for the joint being tight.

The assembly then has no clamping force and the parts can move freely.

Adding a washer takes up a small excess; a significantly long screw has to be changed.

Through-tapped standoffs remove the problem entirely, at the cost of a screw that can protrude into the other side.

With a rod or a spare screw - it takes seconds and settles the screw length question.

Pushing a rod in and marking it where it meets the face gives the usable depth directly.

Manufacturers state thread depth, but stock may vary between suppliers for the same nominal part.

The usable length for the screw is that depth minus a small allowance, plus whatever thickness the screw passes through.

Where a batch is being assembled, checking one part and then buying screws to suit is the efficient order of operations.

Blind and through tappings look identical from the outside, so the check also identifies which has been supplied.

The body is the same; what differs is that both ends depend on screw thread engagement rather than one being an integral stud.

An integral male stud is generally the stronger connection, since it is formed from the standoff itself.

A screwed connection depends on engagement depth and on the screw's own grade.

In practice both are far stronger than the light panel loads standoffs normally carry.

Side loading puts the body into bending in both types equally.

Where load matters, engagement depth and material choice affect the result more than the thread arrangement does.

Only in a through-tapped one - in a blind-tapped standoff they meet solid material first.

Through-tapped standoffs have a continuous thread from end to end, so two screws can meet without either bottoming against the body.

Screws butting against each other still stop turning, so it is not a solution to over-long screws, only a different failure point.

Blind tappings leave a solid section in the middle, which makes the standoff stiffer in bending.

For most applications the difference is unimportant provided screw lengths are correct.

Where screw lengths cannot be controlled, through-tapped is the more tolerant choice.

Hex for handling, round for clearance and appearance - and material on the same load and isolation basis as any standoff.

Because neither end is tightened by turning the standoff itself, the case for hex flats is weaker than with male-female types.

Round bodies therefore appear more often in this type, particularly in visible assemblies.

Brass and steel carry more thread load; nylon isolates electrically and strips at much lower torque.

Stainless suits demanding environments; aluminium is light and machines well.

In a mixed-metal assembly, a polymer standoff breaks the galvanic path that a metal one would create.

Between two panels of the same assembly - enclosures, displays, guards and mounting plates.

Any pair of parts that both have clearance holes suits this type without further preparation.

Display and signage work uses them because nothing projects and the standoff can be decorative.

Guard and cover mounting benefits from the reversibility and the clean surfaces when dismantled.

Single-gap electronics mounting uses them where a stack is not being built.

Multi-layer assemblies generally revert to male-female standoffs for the chaining.