Tom Frost, along with Yvon Chouinard, designed and engineered the first artificial chocks manufactured in North America. The initial chocks were straight-sided, but later evolved into curved-sided nuts to better fit irregular placements. Around 2004, Frost re-introduced the straight-sided, tapered design with the Sentinel Nut. Sentinel Nuts came in two lengths, a standard-length cable versioin and a longer cable version designed to save the use of a sling or a quick draw.

Sentinel Nuts are easier to remove than curved or offset nuts, and Frost claimed that they were more secure. The nearly strait-sided taper also makes determining the quality of the placement easier, an especially nice feature for beginners. Frost claimed that the strait-sided Sentinel Nuts were more secure than curved nuts. I believe that this depends on the specific placement, and that ths choice between straight- and curved-sided nuts should consider the characteristics of the rock where they will be used.

↑ Set 845-853: Frost Works Sentinel Nuts; #1–#9 Long

• Made in USA [ca. 2010].
• Long version that gives extended reach.

↑ 845: Frost Works Sentinel Nut; #1 Long

• Made in USA [ca. 2010].
• Size: 6x9 mm.
• Weight: 18 g.
• About 100 mm. longer than regular version.
• No marking on nut.
  GrayColored heat shrink is printed with "Sentinel," "1," and "4 kN.".
• Mild end taper to accommodate flaring cracks.

↑ 846: Frost Works Sentinel Nut; #2 Long

• Made in USA [ca. 2010].
• Size: 7x11 mm.
• Weight: 20 g.
• About 110 mm. longer than regular version.
• No marking on nut.
  PurpleColored heat shrink is printed with "Sentinel," "1," and "5 kN.".
• Mild end taper to accommodate flaring cracks.

↑ 847: Frost Works Sentinel Nut; #3 Long

• Made in USA [ca. 2010].
• Size: 8x12 mm.
• Weight: 40 g.
• About 115 mm. longer than regular version.
• No marking on nut.
  BlueColored heat shrink is printed with "Sentinel," "1," and "9 kN.".
• Mild end taper to accommodate flaring cracks.

↑ 848: Frost Works Sentinel Nut; #4 Long

• Made in USA [ca. 2010].
• Size: 10x15 mm.
• Weight: 43 g.
• About 115 mm. longer than regular version.
• No marking on nut.
  GreenColored heat shrink is printed with "Sentinel," "1," and "910 kN.".
• Mild end taper to accommodate flaring cracks.

↑ 849: Frost Works Sentinel Nut; #5 Long

• Made in USA [ca. 2010].
• Size: 12x17 mm.
• Weight: 46 g.
• About 115 mm. longer than regular version.
• No marking on nut.
  YellowColored heat shrink is printed with "Sentinel," "1," and "910 kN.".
• Mild end taper to accommodate flaring cracks.

↑ 850: Frost Works Sentinel Nut; #6 Long

• Made in USA [ca. 2010].
• Size: 15x20 mm.
• Weight: 52 g.
• About 115 mm. longer than regular version.
• No marking on nut.
  OrangeColored heat shrink is printed with "Sentinel," "1," and "910 kN.".
• Mild end taper to accommodate flaring cracks.

↑ 851: Frost Works Sentinel Nut; #7 Long

• Made in USA [ca. 2010].
• Size: 18x24 mm.
• Weight: 56 g.
• About 115 mm. longer than regular version.
• No marking on nut.
  RedColored heat shrink is printed with "Sentinel," "1," and "910 kN.".
• Mild end taper to accommodate flaring cracks.
• Hollow core design to reduce weight.

↑ 852: Frost Works Sentinel Nut; #8 Long

• Made in USA [ca. 2010].
• Size: 21x28 mm.
• Weight: 64 g.
• About 115 mm. longer than regular version.
• No marking on nut.
  BrownColored heat shrink is printed with "Sentinel," "1," and "910 kN.".
• Mild end taper to accommodate flaring cracks.
• Hollow core design to reduce weight.

↑ 853: Frost Works Sentinel Nut; #9 Long

• Made in USA [ca. 2010].
• Size: 25x32 mm.
• Weight: 73 g.
• About 115 mm. longer than regular version.
• No marking on nut.
  Dark GrayColored heat shrink is printed with "Sentinel," "1," and "910 kN.".
• Mild end taper to accommodate flaring cracks.
• Hollow core design to reduce weight.