Von Duprin 377T Thumbturn Control Trim

The Von Duprin 377T is the thumbturn control trim from the 370 Series, designed as outside entry trim for the 8827 surface vertical rod exit device and other 88 Series exit devices. If you've been searching for "377t" or "377 t" as a Von Duprin part number, this is the product. It's the outside trim component that gives a keyed thumbturn control on the pull side of a surface vertical rod opening, allowing authorized users to rotate the thumbturn and retract the vertical rod latches for entry.

How the 377T Works

The 377T operates on ANSI Function 11 or 12, which are field selectable. In the standard Function 11 configuration, a key is required to lock and unlock the thumbturn from outside. When unlocked by key, the thumbturn rotates and retracts the latch mechanism on the 8827 device, allowing the door to be pulled open. When the key-locks the thumbturn, it cannot be rotated and the door cannot be opened from outside except by pressing the exit device pushbar from inside.

This is the correct trim for an opening where the outside has a thumbturn instead of a lever. The thumbturn retracts the vertical rod latches but does not itself pull the door open. A separate pull trim or pull handle is needed alongside the 377T for outside entry, which is why the 377T is frequently ordered with DT (dummy) trim or a surface-mounted pull. Both pieces together form a complete outside trim assembly on the 8827.

Night Latch Field Conversion

The 377T ships with an NL (Night Latch) cylinder plate included. This allows the trim to be field-converted to ANSI Function 12, the Night Latch mode, without ordering additional parts. In Night Latch mode, the thumbturn is permanently inoperative from outside. Entry is possible only by turning the key, which momentarily retracts the latch to allow pull entry. When the key is removed, the thumbturn locks again automatically. This is the correct specification for a secured perimeter door where the outside should not have a freely operable thumbturn during normal business hours.

Device Compatibility

The 377T is the 88 Series thumbturn control trim for the 8827 Surface Vertical Rod (SVR) and 8827-F fire-rated SVR exit devices. It is part of the broader 88 Series trim family from Von Duprin. For other Von Duprin exit device families, different thumbturn trim part numbers apply: the 374T is for 98/99 Series devices, and the 376T is for the 55 Series. If your exit device is a different series, confirm the correct trim before ordering.

Physical Specifications

The escutcheon is forged brass at 7/8" (22mm) thick. Base size is 7-1/2" h x 1-11/16" w x 7/8" d (190mm x 43mm x 22mm). Projection is 1-13/16" (46mm). The trim is non-handed. Door thickness is 1-3/4" standard.

Cylinder Requirement

The 377T requires a 1-1/4" mortise cylinder. The cylinder is not included and must be ordered separately. Rim cylinders are not compatible with this trim. Confirm your key system and cylinder type before ordering. If a cylinder is not needed on the outside (for an exit-only application with thumbturn appearance only), specify the 377T-BE blank escutcheon version instead.